Kidush
In the Alter Rebbe's Shulchon Oruch, (271:2) the Alter Rebbe writes that there is a Mitzvah Min HaMuvchar, a preferred Mitzvah, that one should make Kiddush on Friday evening as close as possible to when Shabbos begins, and not to delay the time of Kiddush. However, the Alter Rebbe mentions that if someone does not have an appetite to eat, he does not have to rush to make Kiddush.
It is important to make the Shabbos Kiddush and to eat the Seudah of Shabbos LeTeiovon, with an appetite, and therefore if a person is not in the mood of eating just yet, they should rely on the fact that they already made Kiddush during Davening, which is the Min HaTorah Kiddush, and that later on they can make the DeRabonon Kiddush - Kiddush on a cup of wine - when they have an appetite and wish to eat.
Similarly, there are people who would like to have a Shiur after Maariv and stay in Shul a bit longer before going home. In this case, Poiskim mention that of course they may have a Shiur and then later come home to make Kiddush.
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