Brachot on Food One Eats Before a Meal
If one eats before a meal in a number of cases one is exempt from making a Bracha Achrona because it is exempted by the Birkat HaMazon after the meal. In other cases, though, the foods are not exempted and require a Bracha Achrona as usual. Lastly, in the cases where there is a dispute as regards to the halacha, one should be strict to avoid that situation. See further for details.
Exempting Other Foods
- If someone is eating foods before a meal and the same food in the meal he should have in mind that the food before the meal is going to exempt the food during the meal. Consequently, the food before the meal is connected to the meal and birkat hamazon will cover it, therefore it doesn't need a bracha achrona.
Whetting Your Appetite
- If someone is eating food before a meal to whet his appetite many poskim hold that the birkat hamazon covers those foods even prior to the meal and as such one should not recite a bracha achrona. However, since this is a dispute one should avoid eating more than a kezayit before the meal. Examples of this include wine, liquor, or salty foods before a meal.
- This exemption only works if one eats these foods immediately before the meal, such as within fifteen minutes.
- If one drinks a drink before a meal one should not make a bracha achrona if one is going to drink during the meal. If one is not going to drink during the meal one should recite a bracha achrona.
- However, wine and other liquors whet a person's appetite and don't require a bracha achrona before the meal.
- According to Ashkenazim, if a person ate Pat Haba Bekisnin such as cake before the meal since birkat hamazon might cover the Pat Haba Bekisnin no bracha achrona is recited on the cake before the meal. Some Ashkenazim argue to make a bracha. According to some Sephardim, a bracha achrona is made on Pat Haba Bekisnin before a meal.
- On non-Pat Haba Bekisnin mezonot such as cooked mezonot one should recite a bracha achrona on that food before the meal unless one is going to eat that same food in the meal.
- If someone makes kiddush it certainly does not require a bracha achrona as it is exempted by the birkat hamazon either because of it is halachically linked to the meal or because it whets one's appetite.
- If someone makes havdalah over wine before melava malka and is going to drink more wine during the meal he doesn't need to make a bracha achrona. If someone isn't going to drink more wine during the meal he should recite a bracha achrona.
- If a person drinks wine before a meal one should not make a Al Hagefen afterwards. However, because there is a dispute whether the wine is exempted by the Birkat HaMazon it is proper to avoid this situation by either by drinking a melo lugmav and not a reviyit, having intent when saying Birkat HaMazon that it should cover the wine, or have intent that one's Hagefen upon the wine before the meal should exempt the wine that one drinks in the middle of the middle as long as one does have wine in middle of the meal. 
- Regarding Kiddush, according to Ashkenazim it's preferable to drink a Melo Lugmav and not a Reviyit. According to Sephardim, it's preferable to drink a Reviyit and have intent that the Birkat HaMazon should exempt the wine.
- Mishna Brurah 176:2:1, Vezot Habracha (p. 80). Igrot Moshe 3:33 elaborates that the food before the meal exempts the food in the meal even though one actually intended to eat that food and enjoy it as long as one also had intent to exempt the food in the meal since it is then connected to the meal. See Talk page that in fact this ruling of the Mishna Brurah follows the Tosfot, Rosh, Baal Hameor, Shulchan Aruch, and Magen Avraham, but the Ramban holds that a bracha achrona should be made even if the food would have exempted foods in the meal.
- Mishna Brurah 176:2:3
- Shaar Hatziyun 176:9
- Rosh (Pesachim 10:24), Mishna Brurah 176:2:3, Vezot Habracha (p. 81). (As a fun fact, the scientific research corresponds with the halacha about what makes your hungrier. See this Huffingtonpost.com article or Health.com article).
- Mishna Brurah 174:24
- Vezot Habracha (p. 81)
- Mishna Brurah 174:25, Vezot Habracha (p. 82). The Magen Avraham 174:14 writes that according to those who require a bracha rishona on drinks in a meal the drink before the meal is coming to exempt the bracha of the drinks in the meal and as such doesn't require a bracha achrona. Additionally, according to the Baal Hameor for any drink that one continues to drink in the meal it would not require a bracha achrona since it is considered like one long drinking. Vezot Habracha proves from the Shaar Hatziyun 174:38 that the main reason to accept the Magen Avraham is the first reason and not the second one.
- Biur Halacha 174:6 s.v. v'afilu
- Mishna Brurah 176:2. Biur Halacha explains that since every definition of Pat Haba Bekisnin is questionable whether it is bread and if it is bread then certainly birkat hamazon covers it, one should not recite a bracha achrona on it before the meal.
- Rav Moshe Feinstein in Igrot Moshe 3:33 writes that cakes nowadays are so filled with a majority of sugar, oil, and sweeteners in comparison to the flour that they are certainly Pat Haba Bekisnin. If so, there is no question that they aren't bread and birkat hamazon doesn't exempt them. Therefore, they deserve their own bracha before the meal.
- Vezot Habracha (p. 83) quoting Rav Mordechai Eliyahu
- Mishna Brurah 176:2
- Mishna Brurah 272:35
- Shulchan Aruch 174:4
- Shulchan Aruch 299:8
- Vezot HaBracha (chap 9, p. 84) writes that because drinking wine before a meal involves a dispute one shouldn't make a brahca achrona. However, he quotes three advises from the poskim to avoid this situation. The first is to drink less than a reviyit in order not to become obligated in a bracha achrona. The next is to have in mind when making the Birkat HaMazon that it should exempt the wine one drank before the meal. Lastly, he advises that if one will drink wine in the middle of the meal that one has intent that the hagefen before the meal will exempt the wine in the meal.
- Beiur Halacha 174:6 s.v. Vechen, Vezot HaBracha (chap 8, p 84)
- Or Letzion (vol 2, 20:22)