Hachana is the prohibition of preparing from one Shabbat or Yom Tov to a weekday or to another Shabbat or Yom Tov.
- One may not prepare from Shabbat or Yom Tov for a weekday, a Yom Tov for Chol HaMoed, a Yom Tov for Shabbat, a Shabbat for Yom Tov, from one day of Yom Tov for the second day of Yom Tov, or from one Shabbat for another Shabbat.  It is permitted to prepare on Shabbat for later on Shabbat, and even for Tosefet Shabbat (the extension of Shabbat).
- It’s forbidden to prepare on Shabbat, even for a Mitzvah, if it is happening after Shabbat. 
- Preparation means any action (even speech which isn’t needed for that day), however, if one action is done for both that day and also for after Shabbat it’s permissible. 
- Therefore, it’s forbidden to wash vessels that won’t be needed, prepare food for after Shabbat, fold clothing, or roll the Sefer HaTorah for the next Torah reading. 
- When Erev Pesach falls out on Shabbat, one shouldn’t clean the vessels used for Chametz; rather, one should just wipe them with one’s finger or have a non-Jew do it. 
- When Purim falls out on Motzei Shabbat, one may not bring the Megillah to shul on Shabbat. 
- One may set his bed in order to make the room look presentable. It is forbidden, though, to set a bed in order to sleep on it after Shabbat. 
- After using sefarim on Shabbat, one may return them to the shelf. 
- It’s permissible to go to sleep on Shabbat in order to be awake after Shabbat, however, one shouldn’t say that one is doing so for that purpose. 
- It’s permissible to clear the table even after Seudah Shelishit so that the room looks presentable unless one knows that will not use that room until the end of Shabbat (which is common if Seudah Shelishit finishes late). 
- It’s permissible to do an action that isn’t any extra effort and is commonly done without thinking, so long as long one doesn’t say that he is doing so for after Shabbat. Therefore it’s permissible to take a Tallit home from Shul, return a sefer to it’s shelf, or return food to the refrigerator. 
- It’s permissible an action that doesn’t require extra effort if not doing it will lead to a loss. Therefore if one left clothing outside, one may take it inside to protect it from the rain if there’s a fear that it will rot. 
Studying Torah and other subjects
- It’s permissible to learn Torah on Shabbat even if one is doing so for some need for after Shabbat. 
- Even according to those who permit learning secular subjects on Shabbat (see Permitted and forbidden things to read on Shabbat), many forbid studying for a test during the week. 
- If you learned something and want to mark where it was you can fold over the paper and it isn't considered hachana.
Washing plates, cups, or utensils
- One may not wash plates or other utensils that were dirtied unless there is a chance that they will be used later that day. After Seudah Shelishit one should not wash the plates unless it is clear one will use them on Shabbat. It is permitted to wash drinking glasses unless the glasses certainly will not be used later that day. 
- One may not clean plates or utensils that were dirtied unless there’s a chance that they will be used later that day; nonetheless, one doesn’t have to calculate how many of that utensil will be needed; if one will need even one of a certain type of vessel one may clean many of that same type. One may clean cups because they are frequently used even not at the time of a meal unless one knows that one will not use it that day. 
- After the Friday night meal, one may clean the dishes in order to use them for Shabbat day meal. However, after Seudat Shelishit one may not clean the dishes even if one will be using them the next day. 
- If the dirty pots might become insect infested or may become ruined such as if it is silver, one may let it soak in water even if one doesn’t plan on using them later that day. But one should not clean them. 
- If one removed food from a pot and there’s leftovers still on the sides one may soak the pot in water in order to prevent the leftovers from becoming stuck to the pot, however, if the leftovers already dried onto the pot then it’s forbidden to soak it because one is just doing so in order to make cleaning it after Shabbat easier. 
- It is permitted to put dishes directly into a dishwasher on Shabbat and it isn't considered preparing for after Shabbat.
Heating water on Yom Tov
- One may use hot water in order to clean dishes on Yom Tov (if those utensils will be used on that day), however, it’s preferable to heat up the water before Yom Tov. However, dishes that were dirtied before Yom Tov one shouldn’t heat up water in order to clean those dishes. 
- One may use dishwasher soap in cold water, however, one shouldn’t put dishwasher soap into hot water (even a Kli Sheni). 
- One may use soap in hot water which is in a Kli Sheni but one shouldn’t put soap into a Kli Rishon or have water from a Kli Rishon poured upon it. 
Preparing Food for after Shabbat
- Some poskim permit taking food out of a freezer on Shabbat for a mitzvah meal after Shabbat in the event that it wouldn't be able to be ready after Shabbat unless it was taken out earlier. Additionally, it is only permissible according to these opinions if it is done in a inconspicuous fashion. The same is relevant for preparing from Shabbat to Yom Tov or one day of Yom Tov to another. Other poskim hold that it is forbidden.
- It is permitted to put back leftovers to a refrigerator on Shabbat to prevent them from spoiling.
- A parent may dress his young children in pajamas even if the children will be going to bed after Shabbat is over if this is the normal time for them to get into pajamas on every other day. 
- ↑ Shulchan Aruch 503:1, Kitzur Shulchan Aruch 101:1, Shemirat Shabbat KeHilchata 28:69.
- The Mishnah (Shabbat 113a) writes that one may fold clothing on Shabbat. Rashi (s.v. Afilu) limits this to where one is folding the clothes in order to wear them again that day. Tosfot (s.v. Mekaplin) infers that it would be forbidden to fold clothing that would be needed only after Shabbat. This is codified by the Rif 41b, Rambam 22:22, Rosh 15:2, Tur, and S”A 302:3. From this and other halachot, the poskim explain that in general there is a Rabbinic prohibition of preparing on Shabbat for the weekday (See Orchot Shabbat vol 2, p. 400).
- In explaining the concept of Hachana, the Rambam (Shabbat 23:7) writes that cleaning dishes that one does not need to use on Shabbat is considered Metaken, whereas the Raavad argues that it is prohibited because it involves exerting effort for something that is needed during the week. Nonetheless, the Maggid Mishneh and Migdal Oz explain that the Rambam agrees with the Raavad and that his intention was that it is an issue of fixing the dishes for after Shabbat. Tzitz Eliezer 14:37 writes that this also is the opinion of Rashi.
- ↑ Sh”t Minchat Shlomo Tinyana 36:10 writes that there is no prohibition of preparing from Shabbat to Tosefet Shabbat because even Tosefet Shabbat is called “Yom HaShabbat HaGadol HaZeh” in Birkat Hamazon. Orchot Shabbat (vol 2, p. 408) agrees.
- ↑ Shemirat Shabbat KeHilchata 28:69
- ↑ Shemirat Shabbat KeHilchata 28:70
- ↑ Shemirat Shabbat KeHilchata 28:71
- ↑ Shemirat Shabbat KeHilchata 28:71
- ↑ Shemirat Shabbat KeHilchata 28:75
- The Mishnah (Shabbat 113a) writes that one may set one’s bed on Friday night for Shabbat day but not on Shabbat for Motza’ei Shabbat. The Rif 41b, Rambam 23:7, Rosh 15:2, and Magen Avraham 302:6 codify this rule. Magen Avraham adds that one may set one’s bed so that the room will look presentable because that is considered a need for Shabbat. Mishna Brurah 302:19, Shemirat Shabbat KeHilchata 28:86, and The 39 Melachos (vol 1, p. 121) agree. The Machzik Bracha 302:2 points out that this is only when people will pass by the area where the beds are, but if the beds are in a separate room which people don’t pass by one may not set the beds. Kaf HaChaim 302:23 agrees.
- Similarly, Magen Avraham 667:3 writes that when taking out tables from the Sukkah on the last day of Sukkot one may not set up the table for Shemini Aseret, however, one may stand up the table for Kavod Yom Tov. Pri Megadim E”A 667:3 explains that the general rule is that if the activity is done so that the house doesn’t look like a wreck it’s permitted, but if not, it’s forbidden.
- Similarly, Sh”t Igrot Moshe 4:47 rules that it is permissible to place one’s dirty dishes from the meal into a dishwasher on Shabbat even though it makes it easier to start the dishwasher after Shabbat if one is doing so in order that the dirty dishes don’t make the house look like a mess. He adds that one should just put each dish in the dishwasher as it come to his hand rather than sorting them as usual. Yalkut Yosef (vol 2, p. 221) agrees.
- ↑ Shemirat Shabbat KeHilchata 28:89 quotes Rav Shlomo Zalman’s opinion that an action that doesn’t involve any Melacha, isn’t a Tircha (excessive effort), and is usually done without thinking may be done on Shabbat even if it has an effect for after Shabbat. For example, he permits bringing a Tallit home from shul and returning a sefer to the shelf after using it. He adds (chapter 3 note 239) that in a shul, it is proper for each person to return his siddur and chumash to the shelf because if the gabbai has to return all the sefarim, it may involve Borer. Yalkut Yosef (vol 2, p. 226) agrees. Rabbi Mordechai Willig (Am Mordechai p. 176), however, questions the Shemirat Shabbat KeHilchata’s premise and concludes that one should be strict regarding bringing the Tallit home. The 39 Melachos (vol 1, p. 116) agrees that returning one or two sefarim is permitted but returning many siddurim and chumashim in shul at the end of Shabbat is forbidden because it is clearly done as a preparation for after Shabbat.
- ↑ Shemirat Shabbat KeHilchata 28:72
- ↑ Shemirat Shabbat KeHilchata 28:79
- ↑ Shemirat Shabbat KeHilchata 28:81
- ↑ Shemirat Shabbat KeHilchata 28:83
- ↑ Shemirat Shabbat KeHilchata 28:84 (in new editions 92), 39 Melachos (vol 4, pg 982), Yalkut Yosef (Shabbat, vol 2, pg 216)
- Shemirat Shabbat KeHilchata (chap 28, note 206 and in new editions 220) quotes Rav Shlomo Zalman who was in doubt regarding whether it’s considered Hachana to study secular subjects not for the knowledge but only to do well on a test during the week. 39 Melachos (vol 4, pg 982) rules that it’s forbidden because of Hachana.
- Yalkut Yosef (Shabbat, vol 2, pg 216) rules that one may only learn Torah on Shabbat and the only exception is a medical student who has a test after Shabbat and is pressured for time to study medicine (except for the study of surgery) on Shabbat. Though in that one case where it is permissible to learn secular studies on Shabbat it is only permitted with regards to Hachana.
- However, Rav Aviner permits study for a test on Shabbat if one enjoys the learning and doesn't cause one stress.
- ↑ Shemirat Shabbat Kehilchata 28:16. See Judaism.stackexchange.com.
- The Gemara (Shabbat 118a) quotes a Braita which establishes that that one may wash dishes on Friday night for use on Shabbat morning, on Shabbat morning for use on Shabbat afternoon, and on Shabbat afternoon for use at Mincha time, but one may not wash them after Mincha time. The Braita adds that cups may be washed anytime, because there is no fixed time for drinking. The Rif 44a, Rambam 23:7, and S”A 323:6 cite this Braita.
- The Rosh 16:5 leaves out the case of cleaning on Shabbat morning for use on Shabbat afternoon. The Tiferet Shmuel explains that the Rosh left out that phrase because he understood that the Braita followed Rabbi Chidka’s opinion that one should eat 4 meals on Shabbat, and the Rosh emended the Braita according to the halacha that one needs to eat only 3 meals on Shabbat. However, Tiferet Shmuel wonders why the Rosh didn’t explain the Braita as saying that one may clean the dishes for a voluntary meal in the afternoon. In fact, the Tosfot Rid 118a explains that the Braita is describing a person who wants to eat a voluntary fourth meal. Additionally, the Korban Netanel explains that the Rif 44a agrees with the Tosfot Rid, as the Rif quotes the Tosefeta including all 4 meals. The Me’iri 118a, however, rules that one may clean his dishes only in order to eat one of the 3 obligatory meals of Shabbat and not in order to eat a fourth meal.
- The Pri Megadim E”A 323:9 implies that the general rule is that if one knows that he will use these dishes again on Shabbat, he may clean them, and if he knows that he will not use them again on Shabbat, he may not clean them. Someone who is unsure if he will use them later may not clean the dishes after Seudah Shelishit, since there is no assumption that he will use them again. Mishna Brurah 323:28, Kaf HaChaim 323:42, and Shemirat Shabbat KeHilchata 12:1 agree. Although Rav Ovadia Yosef in one place (Leviyat Chen p. 103) cites the Me’iri and rejects the Pri Megadim’s ruling that one who is sure that he will have a voluntary meal may clean his dishes, in Yabia Omer 7:37:6 he retracted and agreed with the Mishna Brurah.
- Ketzot HaShulchan 146:16 writes that one may clean dishes that are used for fruit or snacks at anytime as long as it is not clear that he will not use it again, since these utensils are similar to drinking glasses. Shemirat Shabbat KeHilchata 12:1 agrees.
- The Tosefta 13:19 concludes that one may clean ten cups even if he needs only one, because each one is perfectly fit to be used. This is codified by the Magen Avraham (323:8, quoting the Rokei’ach) and Mishna Brurah 323:26. Shemirat Shabbat KeHilchata 12:1, Mishneh Halachot 3:40, and Menuchat Ahava (vol 1, 11:5) apply this leniency both to cups and dishes. See, however, Bnei Tzion 323:9, who argues that this Tosefta was not quoted by the S”A because it was not accepted by the Bavli. He adds that even if applies to cups, it certainly doesn’t apply to dishes.
- Aruch HaShulchan 323:7 writes that if one has sufficient dishes or cups for the rest of Shabbat, it is improper to clean anything. Tosfet Shabbat 323:8, Kaf HaChaim 323:39, Shevet HaLevi 5:39 and 6:42, Bear Moshe 6:82, Yalkut Yosef (vol 4, p. 21), and Menuchat Ahava (vol 1, 11:4) agree. Mishneh Halachot 3:40 and 6:80, however, permits cleaning the dishes for a Shabbat meal even if one has other dishes, because in essence one is cleaning for the purpose of Shabbat and not for the weekday. Rav Moshe Feinstein (cited in Kol Torah vol 54 p. 18), Rav Nissim Karelitz (cited by Orchot Shabbat p. 404), and Brit Olam (p. 66) agree.
- Bnei Tzion 323:9 brings a proof to the Aruch HaShulchan from a halacha in regards to folding clothes. The Mishna (113a) writes that one may fold clothes on Shabbat, but the Gemara limits this to a case where one doesn’t have any other clothes. The Raavan (Chap 15) explains that if one were to have other clothes, folding one’s clothes would be considered preparing for after Shabbat. Similarly, the Biur HaGra also explains that this is the source for Rashi’s claim that one may only fold clothes if one needs to wear them again on Shabbat. The Ri (Tosfot 113a s.v. Yesh) has a doubt whether a person who has other clothes which aren’t as nice as the ones he wants to fold is allowed to fold his clothes or not. The Mishna Brurah 302:17 and Kaf HaChaim 302:29 rule that it is forbidden to fold clothes even if the other clothes aren’t as nice. Nonetheless in Shaar HaTziyun 302:17 he adds that the clothes which one wouldn’t wear on Shabbat aren’t considered a valid alternative, which would prevent one from folding one’s clothes.
- ↑ Shemirat Shabbat KeHilchata 12:1
- ↑ Shemirat Shabbat KeHilchata 12:1
- ↑ Shemirat Shabbat KeHilchata 12:2, Mechezeh Eliyahu 64:23
- ↑ Shemirat Shabbat KeHilchata 12:3, Mechezeh Eliyahu 64:23
- ↑ Mechezeh Eliyahu 64:36
- ↑ Shemirat Shabbat KeHilchata 12:4
- ↑ Shemirat Shabbat KeHilchata 12:5
- ↑ Shemirat Shabbat KeHilchata 12:6
- ↑ [Mechezeh Eliyahu 64:35 http://www.hebrewbooks.org/pdfpager.aspx?req=21547&st=&pgnum=210] and Chazon Ovadia Shabbat v. 2 p. 447. Mechezeh Eliyahu adds that if it is an item that will defrost and a puddle of water will pool beneath it then it should be placed in a container with water in it so that the defrosted water is nullified by the water in the container.
- ↑ Rav Shlomo Zalman Auerbach in Shulchan Shlomo 290:13 cited by Chazon Ovadia
- ↑ Mechezeh Eliyahu 64:24
- ↑ Dinei Chinuch Katan pg. 190