It should consist primarily of practical instructions concerning the observance of the coming festival; if the Rabbi speaks only in "Pilpul" (intricate Talmudic analysis) or homiletics, he has not properly fulfilled this obligation (Mishna Berura 429:2).
Strictly speaking, a person is considered a resident of the city for this purpose only if he has lived there for twelve months or more (Rama 429:1). However, the Mishna Berura (429:5) cites from earlier sources that the common practice is to consider a resident a permanent member of the community for this purpose once he has resided there for a period of thirty days. Furthermore, he writes, if it is clear that somebody plans on residing in the community permanently, he is considered a resident immediately.
The Mishna Berura (429:5) writes that although the custom of Ma'ot Chitim does not require providing him with flour for Matzot, the standard rules of charity apply, requiring the community to provide him with enough Matza for two meals each day, and for three meals on Shabbat.
The Shulchan Aruch (429:2) forbids the observance of a communal fast during Nissan, but allows individuals to observe a private fast. The Rama (429:2), however, records the practice to forbid even private fasts during the month of Nissan, including Erev Rosh Chodesh Iyar, even for those accustomed to fasting on Erev Rosh Chodesh (Mishna Berura 429:10).
The section of the "Nesi'im" (Bamidbar 7:1-8:4), which tells of the special gifts and offerings brought by the twelve tribal leaders for the inauguration of the Mishkan. Each day starting from Rosh Chodesh Nissan, one reads of the offering brought on that day, and on the thirteenth of Nissan, one reads the opening verses of Parashat Beha'alotecha (Mishna Berura 429:8).