==First Night of Sukkot==
# There is an obligation to eat a Kezayit of bread in the Sukkah on the first night of Sukkot.<ref>The Rabbis in the Mishna (Sukkah 27a) hold that there is an obligation to eat in the Sukkah on the first night and afterwards it is optional to eat in the Sukkah. The gemara explains that the reason for the Rabbis is that there is a gezerah shava between Sukkot and Pesach and just like there is an obligation to eat Matzah on the first night of Pesach, so too there is an obligation to eat bread on the first night of Sukkot. This is codified by the Rambam (Sukkah 6:7) and S"A 639:3.</ref> According to many rishonim, there is an obligation to eat a meal in the Sukkah each day and night of Yom Tov.<ref>The Gemara Brachot 49b states that on Yom Tov one would have to repeat Birkat HaMazon if one forgot to say Yaaleh VeYavo because there is an obligation to eat a meal. The rishonim point out that this seems to be at odds with the gemara Sukkah 27a which says that it is optional to have a meal on Sukkot other than on the first night.
* Some rishonim answer that there is an obligation to eat a meal each day and night of Yom Tov because of Yom Tov, but the obligation unique to the Sukkah is just the first night. If so, what's the difference between the obligation to eat a meal due to the fact that it is Yom Tov and the obligation to eat a because of the Sukkah? Rabbenu Yehuda (Tosfot Brachot 49b s.v. Iy) answers that if it rains and one has to eat inside, if the obligation is just because of Yom Tov one would fulfill one's obligation. However, if the obligation is because of the Sukkah one would have to eat in the Sukkah anyway after the rain stops.
There is a small discrepancy between the Rosh 's (Brachot 7:23) version of Rabbenu Yehuda , in which he states that one should eat one's meal in the rain as opposed to waiting until the rain stops. * Alternatively, the Ritva (Sukkah 27a s.v. VeShiur) quotes his Rebbe as explaining that while one can fulfill the regular Yom Tov meal by eating a Kezayit of bread outside the Sukkah, the first night meal needs to be eaten in the Sukkah even if it is only a Kezayit. Tur 639:3 agrees. Both answers are quoted by the Ran (Sukkah 12b).* Other rishonim answer simply that the Gemara Brachot which said that it is an obligation to eat a meal on Yom Tov was only referring to the first nights of Pesach and Sukkot. However, there's no obligation to eat a bread meal the rest of the days of Pesach and Sukkot. This is the opinion of the Tosfot (Sukkah 27a s.v. Iy) and Rashba (Brachot 49b s.v. Tefillah) . According if it rains on the first night, one wouldn't have to eat in the Sukkah. Such is the opinion of the Rashba ( Teshuva) and Or Zaruah.</ref>
# On the first night of Sukkot, one should wait to do [[Kiddish]] until after [[Tzet HaKochavim]]. However, after the fact if one made [[Kiddish]] during [[Bein HaShemashot]] and ate a [[Kezayit]] of bread one should make sure to have another [[Kezayit]] after [[Tzet HaKochavim]] but one doesn’t need to make another Bracha of LeShev BaSukkah. <ref>Rama 639:3 writes that one make sure not to eat until nighttime. Mishna Brurah 639:25 explains that this is based on the connection between [[Pesach]] and [[Sukkot]] and by [[Matzah]] one may only eat at night as it says in the פסוק. Mishna Brurah continues that after the fact if one ate one should eat another [[Kezayit]] but not make another LeShev BaSukkah because of [[Safek Brachot LeHakel]]. Natai Gavriel ([[Sukkot]] 38:12) extends the Rama to not even making [[Kiddish]] before nighttime. Yalkut Yosef (Moadim pg 138) agrees with the above halachot. </ref>
# On the first night of [[Sukkot]] the Bracha of [[Shehecheyanu]] should be said after [[Kiddush]]. <ref>S"A 643:1 </ref>After the fact if one made [[Shehecheyanu]] before [[Kiddish]] one fulfilled one's obligation (and one shouldn't go repeat it after [[Kiddish]]). <ref>Mishna Brurah 643:3 </ref>