Before the Bracha
This is the approved revision of this page, as well as being the most recent.
Physical preparations of one's body
- When reciting a bracha, one's mouth should be empty so that one can fully praise Hashem. 
- One must wear a Kippah while making a Bracha.  If one doesn't have a Kippah one should cover your head with your hand and a little bit of your sleeve or ask a friend to cover your head with his hand (even without a sleeve). 
- One should be dressed properly before making any bracha especially Birkat HaMazon 
- One should figure out which bracha one has to make before one begins to say the bracha so that one can have the proper intent when one says Hashem's name.
- One should be careful to make brachot with kavana (the proper intent) thinking about blessing with hashem's name, who granted us great kindness in allow one the fruit or bread one has or that he commanded one to perform a mitzvah that we are about to perform. Thus, a person should make the bracha slowly and loud out in order to inspire the requisite kavana. 
- One should not recite a bracha if one needs to go to the bathroom. Some say that it is permitted if one can hold it in for 72 minutes and others say it is forbidden.
- Making brachot in front of an ervah has the same halacha as learning Torah. See Laws_of_Learning_Torah#Learning_in_Front_of_Ervah.
- Making brachot in an unclean place has the same halacha as learning Torah. See Laws_of_Learning_Torah#Learning_in_an_Unclean_Place.
Preparation of the food
- One should only make the Bracha only after one has the food available and present so that the Bracha can take effect on something. Therefore, one should open the packaging of the food prior to the Bracha. 
- One should hold the food that one is making the bracha upon. After the fact, one doesn't need to repeat the bracha.
- One who drinks from a water-fountain, ideally, should have the water in a cup prior to the Bracha, however if that’s not possible, one should let the water run from the faucet momentarily prior to making the Bracha. If that last option isn’t possible or one is concerned about wasting water, he may make the Bracha on the water even before letting it run. 
- One should prepare the food before making a bracha; for example, one should break open a nut or peel a fruit in order to eat it right after the Bracha. 
- However, one shouldn't cut a large or whole piece of food before the bracha; for example, one shouldn't cut a fruit, or a piece of meat before the bracha, rather make the bracha and then cut it. 
- Gemara Brachot 50b writes that if one forgot and put food into one's mouth, if the food isn't something that's easily ruined it should be spit out. On this the gemara explains that one should spit it out so that one could have his entire mouth involved in praising Hashem based on the pasuk ימלא פי תהלתך (Tehillim 71:8). The Shulchan Aruch 172:2 rules like this gemara and the Kitzur Shulchan Aruch 6:2, Mishna Brurah 172:7, Kaf HaChaim 172:4, and Vezot HaBracha (p. 7) concur.
- Shulchan Aruch 91:3
- Shulchan Aruch 91:4 writes that using one's hand to cover one's head isn't sufficient for a head-covering, but a friend covering one's head would be sufficient. Mishna Brurah 91:10 adds that it is considered a head-covering if one uses one's hand along with a bit of the sleeve.
- Shulchan Aruch 74:4 writes that one should cover one's lower body (with pants) even if one's upper body is revealed prior to saying Shema. Yet, Mishan Brurah 74:22 writes clearly that this is only for extenuating circumstances, otherwise one should always dress properly even for regular brachot and all the more so for Shema. VZot HaBracha (pg 8) quotes Rav Elyashiv that one should dress properly for brachot even by the beach. Or Letzion 13:3 and VeTen Bracha (pg 212) in name of Rav Shlomo Zalman Auerbach say that one must wear proper clothing for Birkat HaMazon just like the requirement of Ituf (see Shulchan Aruch 183:5)
- Kitzur Shulchan Aruch 6:1
- Kitzur Shulchan Aruch 6:1 quoting the Sefer Chasidim
- Rama 92:1
- Mishna Brurah 92:7
- Shaarei Teshuva 6:5
- Mishna Brurah 206:19, VeZot HaBracha (Chapter 1, pg 8)
- Shulchan Aruch 167:3 writes that one should hold the bread while reciting Hamotzei. Mishna Brurah 167:22 explains that the reason for this is that one should make the bracha immediately before performing a mitzvah and not too far in advance.
- Mishna Brurah 167:22 based on Shulchan Aruch 206:5
- Vezot haBracha (Chapter 1, pg 8) based on Mishna Brurah 206:19 who writes that ideally one should have water in a cup so that the food is present during the Bracha. However, if that’s impossible, Rav chaim Pinchas Sheinburg (quoted by Vezot HaBracha) suggests letting the water run prior to the Bracha so that it’s evident what one is making a Bracha on. Lastly, if that’s impossible, one may make the Bracha even while the faucet is closed.
- Mishna Brurah 206:19 writes that one should prepare food before the bracha so that it's ready to eat right after the bracha. Vezot HaBracha (Chapter 1) gives the examples of removing the shells a nut and peeling a fruit.
- Vezot HaBracha (end of Chapter 1) based on Aruch HaShulchan 202:11, and Vezot HaBracha quotes the example of leaving a piece of meat in its full state from Rav Elyashiv and Rav Mordechai Eliyahu.