Halachot from the Ben Ish Hai (Rav Yosef Haim of Baghdad, 1833-1909) in Parashat Nisavim concerning the first night of Rosh Hashana
One should avoid sour foods on Rosh Hashana. Therefore, lemon flavors should not be used. If the pomegranate, which is customarily eaten on the first night of Rosh Hashana, is tart, sugar should be added. In general, on should not eat fruits that are not fully ripe.
It is fitting to eat choice cuts of meat and sweet foods as a good Siman (omen). One should not indulge and eat to his full satiation. Rather, he should merely taste from each of the different foods. Also, he should drink pleasant beverages. This is based on the Pasuk in Ezra that says Ezra instructed the people to eat fatty foods, drink sweet beverages and send gifts to those who do not have.
One should be especially careful not to get angry on Rosh Hashana. Of course this a terrible P'gam (flaw) throughout the year, all the more so, it is a dire omen for the new year if one gets angry on Rosh Hashana. On the first night of Rosh Hashana, the table should be set by the time the husband comes home from Shul. This is considered a good sign for the new year. However, if he comes home and sees that the table is not ready, he should not get into an argument with his wife. He should be patient and not hold it against her, even in his heart.
The Tikun and Kiddush:
Before Kiddush, there are a number of Pesukim and passages recited. He opens with P'Tach Eliyahu, and then says the Pasuk "V'Noach Masa Hen" and "VaYizra Yishak" (Bereshit 26:12) twelve times. Then he says "Ki Imha M'kor Haim" (Tehilim 36:10) ten times. This is followed by "Or Zarua La'Sadik" (Tehilim 97:11) seventeen times and "V'Amartem Koh L'Hai" (Shmuel I 25:6) ten times. After that he says "Tachel Shana U'Birkoteha" (Begin the New Year and its blessings) and then he stands and makes the Kiddush. Much of this is recorded in the Machzorim.
On both nights of Rosh Hashana, the Beracha of Shehecheyanu is recited. If one has a new fruit, which mandates a Shehecheyanu, he should put it on the table on the second night. The Ben Ish Hai's custom was to repeat the entire Seder of Rosh Hashana on the second night as well. Those who want to follow this practice, may do so.
The custom is to study the Mishna of Rosh Hashana, one chapter at each of the four meals. One should have intent that each of the four chapter corresponds to one of the four letters of the divine name ADoNaI. The study should not be rushed. It is also customary to read the passage from the Zohar HaKadosh, which is brought in the Machzorim.
If the woman's Mikveh night is on Rosh Hashana, she should immerse, and they should be together. It is "Hasidut Shel Shtut" (foolish piety) to abstain on her Mikveh night. Even if it is not the night of the Mikveh, if one sees that his desire for his wife is aroused, he may be with her, in order to avoid distraction during the prayers of this holy day. In either case, one should insure that he immerses in the Mikveh the next day before Tefila, so that he prays with holiness and purity.