Terumot and Maaserot
- Nowadays, taking Terumot and Maaserot is only Derabbanan (according to most authorities), but nonetheless, one must make a Bracha upon separating certainly untithed produce. The Bracha is ברוך אתה ה' אלוקינו מלך העולם אשר קידשנו במצותיו וצוונו להפריש תרומות ומעשרות. 
Produce from different years
- One may not take Trumot and Maaserot from produce of one year for produce of another year. If one did take Trumah or Maaser in such a manner one’s action is irrelevant and one must take Trumah and Maaser again properly. 
- In the first, second, fourth, and fifth year of the Shemitta cycle one must take Maaser Rishon and Maaser Sheni. However, in the third and sixth year of the Shemitta cycle one must take Maaser Rishon and Maaser Ani.  During the Shemitta year all the produce of the field is Hefker (ownerless) and so there’s no obligation of take Trumot and Maaserot. 
How is a year counted for Trumah and Maaser?
- For vegetables the year begins on Rosh Hashana, the first of Tishrei. Trumah and Maaser are taken depending on when the vegetables were harvested. 
- For fruit trees the year begins on Tu Beshevat. Trumah and Maaser are taken depending on when the fruit on the trees ripened to the point that it is able to reproduce expect the Etrog for which the Trumah and Maaser are taken depending on when it was harvested. 
- Some say that lemon, golden apple, and other citrus fruit are similar to the Etrog and depend on when they are picked while others argue that they are the same as all other fruit trees which depend on when the fruit has ripened. 
Produce of a non-Jew
- Produce which a non-Jew grew on non-Jewish land and then brought to the market is exempt from Terumah and Maaserot. 
- Produce grown by a non-Jew which a Jew has completed it’s processing is obligated in Terumot and Maaserot. 
- If a non-Jew brought grapes to market and then a Jew bought them to eat or to make wine the grapes are exempt from Terumot and Maaserot unless the non-Jew harvested the grapes in order to make wine in which case if the Jew buys the grapes and makes wine there is an obligation of Terumot and Maaserot. 
- Rambam (Hilchot Terumot 1:26) writes that Terumot and Maaserot is only Derabbanan nowadays, while the Raavad (Hilchot Terumot 1:26) argues that the obligation is Deoritta. The Maggid Mishna (Hilchot Terumot 1:26) writes that most Rishonim hold like the Rambam including the Smag (Mitzvah Aseh #133), Sefer HaTerumah (Hilchot Eretz Yisrael pg 80b), Rashba (Yevamot 82b, Shevuot 16b), Ritva (Yevamot 82a), and Sefer HaChinuch (Mitzvah 507). S”A Y”D 331:2 rules like the Rambam. Nonetheless, the Rambam (Hilchot Terumot 2:16) writes that there is an obligation to make a Bracha upon separating untithed produce even nowadays. S”A Y”D 331:78 and Chazon Ovadyah (Tu Beshevat pg 47-49) agree. This is opposition to the opinion of Shulchan Gavoha 331:15 who contends that since the obligation is only Derabbanan one shouldn’t make a Bracha nowadays.
- Mishnah Trumot 1:5, Rambam (Hilchot Terumot 5:11), S”A Y”D 331:57, Chazon Ovadyah (Tu Beshevat pg 43)
- Gemara Rosh Hashana 12b, Rambam (Hilchot Matanot Aniyim 6:2-4), Chazon Ovadyah (Tu Beshevat pg 47)
- Rambam (Hilchot Aniyim 6:5)
- Gemara Rosh Hashana 12a, Rambam (Hilchot Terumot 5:11), S”A Y”D 331:57, 331:125, Chazon Ovadyah (Tu Beshevat pg 43-4)
- Gemara Rosh Hashana 12a, Rambam (Hilchot Maaser 2:4-5), S”A Y”D 331:57, 331:125, Chazon Ovadyah (Tu Beshevat pg 43-4)
- The Rosh Sirleav (Sheviyit 9:4) holds that lemons are the same as Etrogim regarding Trumah and Maaser. This is also the opinion of the Eshel Avraham Neemark (Sheviyit pg 117b). However, Sh”t Minchat Shlomo 1:51(22), and Shabbat HaAretz (Kuntres Acharon pg 118) argue that Etrog is unique. Chazon Ish (Sheviyit 7:16) writes that since there’s a doubt if these fruits would ripen in the 2nd year (before Tu Beshevat) and be picked in the 3rd year (after Tu Beshevat) [or if these fruits would ripen in the 3rd year and be picked in the 4th year] one should take both Maaser Sheni and then after redeeming the Maaser Sheni one should take also Maaser Ani which should be given to the poor. This is also the opinion of Sh”t Mishpat Cohen 51:2 and Sefer Aser TeAser (pg 546). However, Chazon Ovadyah (Tu Beshevat pg 44-46) argues that in cases of doubt one doesn’t have to give Maaser Ani (and proves it from the Rambam (Maaser Sheni 1:11).
- Rambam (Hilchot Terumot 1:11) and Kesef Mishna (Terumot 1:11). Chazon Ovadyah (Tu Beshevat pg 50-52) codifies this as halacha.
- Rambam (Hilchot Terumot 1:11)
- Chazon Ovadyah (Tu Beshevat pg 52)