Some have the custom to make Kiddush after Kriat Hatorah, before Tekiot. According to Chabad, Ideally, men should not eat before Shofar. If this is difficult, or there is any concern that one will not be able to concentrate during davening, he may eat and drink (preferably not Mezonot). One should not be stringent if there are health concerns.
It is especially appropriate to go to Mikvah before davening. The Chazanim should familiarize themselves in advance with the meaning of all of the Piyuttim and Tefillot – even if they already did so the previous year. Similarly, one should train his children regarding the order of davening beforehand, so as to minimize any distractions during davening.
Some have the custom to wear a kittel for Rosh Hashanah davening, some hold of just the Chazzan, the Ba’al Koreh, and the Ba’al Tokeah, however the Chabad custom is not to wear a Kittel at all on Rosh Hashanah.
Shir Hamaalot (after Yishtabach): Many have the custom to open the Aron Hakodesh, and to recite it verse by verse after the Chazzan. This is not the Chabad custom. However, one should say it with deep concentration and from the heart. When the Aron Hakadosh is opened during Chazarat Hashatz, it is not obligatory to stand, since the Sefer Torah is not being moved. Some have the custom to stand.
At Shacharit, the paragraph of Misod (at the beginning of Chazarat Hashatz) and the one that follows is recited by the Chazzan and not by the congregation. Many stand for the Piyut beginning L’e-l Orech Din, recited in Shacharit on the first day and in Musaf on the second day.
Avinu Malkeinu: Some have the custom to recite part of it verse by verse after the Chazzan, however, it is not the Chabad custom to do so. The words Roa Gzar are recited without pausing in between. It is customary to grant an Aliyah to the Ba’al Musaf, unless he is being paid. A Brit performed at Shul is conducted before Tekiat Shofar. A Brit performed at home is held after davening.
