Month of Nissan
Preparation for Pesach
- Thirty days before Pesach one should start learning the halachot of Pesach.  The 30 days begin from Purim itself.  All the more so, on the holiday itself one should learn the halachot of Pesach. 
- This doesn't mean that a talmid chacham should stop his regular learning to learn halacha of the upcoming holiday, but rather it means that a question about hilchot pesach is given precedence to questions not about pesach.
- Also it is very important for the (local) Rabbi to give shiurim informing people of the halachot of Pesach. 
Tachanun, Fasting, and Eulogies
- There's no Tachanun for the entire month of Nissan. 
- According to Ashkenazim, one shouldn’t fast during Nissan; even an individual who has Yehrzheit shouldn’t fast during Nissan.  However, according to Sephardim, one shouldn’t establish a communal fast during Nissan. However, an individual is permitted to fast, such as for a Yehrzheit during Nissan, except on Pesach and Rosh Chodesh. 
- There aren't supposed to be communal fasts or eulogies during the month of Nissan. 
- A bride and groom the day of their wedding may fast during Nissan even on Rosh Chodesh Nissan. 
- It’s permissible to fast a Tanit Chalom, a fast made to rectify a bad dream, during Nissan. 
- During the first 13 days of Nissan, there is a nice minhag, for the first 12 days to read the Parsha of the Nesiyim for that day (found in Bamidbar 7), and on the 13th day to read the first four pesukim of Parshat Bahalotcha.  The minhag is to read it from a chumash. 
- It’s proper to give Maot Chitim, charity to the poor in order that they have money for Matzah on Pesach. 
- It’s permissible to give Maot Chitim from money of Maaser Kesafim, a tith of one’s money. 
see Shabbat HaGadol
See the Birkat Ilanot page.
- Practices of Nissan by Rabbi Ezra Schwartz
- Halachos for the Month of Nissan by Rabbi Moshe D. Tendler
- In Gemara Pesachim 6a, Rabbanan hold that one should begin to learn Hilchot Pesach thirty days in advance of Pesach, whereas Rabban Shimon Ben Gamliel holds only 2 weeks. Rabbanan learn this idea from Moshe who taught the laws of Pesach Sheni thirty days in advance which was Pesach in Nissan. Shulchan Aruch 429:1 rules like the opinion of the Rabbanan. Mishna Brurah 429:2 writes that it begins on Purim and it’s an obligation upon each individual to learn the Halachot of Pesach in this time.
- Mishna Brurah 429:2. Chazon Ovadyah (Pesach pg 1) agrees that the thirty days before Pesach begins on Purim itself. Nonetheless, he adds that if someone has a question about Pesach and someone has a question about Purim, the question about Purim takes precedence.
- Gemara Megillah 32b states that on Pesach itself, one should learn the halachot of Pesach on Pesach. Mishna Brurah 429:1 and Chazon Ovadyah (Pesach pg 1) quote this as halacha as opposed to Shulchan Aruch HaRav 429:4 who writes that on the holiday itself the Rabbi should speak about the topic of the day, meaning the miracle that occurred and Aggadah because the halachot are easily found in books.
- Yabea Omer 2:22, Chazon Ovadyah (Pesach pg 1) explains that the halacha in Gemara Pesachim 6a is relevant in regards to the laws established in Tosefta Sanhedrin 7:5 which state that a person should ask relevant questions and a relevant question has precedence over the irrelevant questions. Bach 429 writes that this obligation applies even to somebody who has learnt it in the past, because he should refresh his memory.
- Mishna Brurah in Shaar HaTziyun 429:5 points out that the primary teaching on the holiday itself should be halacha and not just the idea of the day. Chazon Ovadyah (Pesach pg 1) writes that it's important for the (local) Rabbi to give shiurim about hilchot pesach. See Kaf HaChaim 429:3 who speaks about the importance of these drashot of the Rabbi and how they should include halacha.
- Shulchan Aruch 429:2 writes that there's no Tachanun for the entire month of Nissan. Mishan Brurah 429:7 explains that since the Nesiyim (in Bamidbar 7) brought the Korbanot for the first 12 days of Nissan, the days were considered a Yom Tov for them. Then Erev Pesach, Pesach, and Issru Chag are connected to Pesach. Altogether since most of the month is related to Kedusha it's all considered Kodesh. Chazon Ovadyah (pg 2) adds that the celebration of the building of the third Bet Hamikdash, which will occur in Nissan and in particular on Pesach, will extend for another week after Pesach. This is also brought down in Shu"t Chatam Sofer 103.
- Rama 429:2
- S”A 429:2, Chazon Ovadyah (Pesach pg 5-7). Or Le’sion (vol. 3, 5:1).
- S”A 429:2. Mishna Brurah 429:9 adds that the minhag Ashkenaz was for even individuals not to fast during Nissan.
- Mishna Brurah 429:10, Halichot Shlomo (Moadim vol 1, 2:3)
- Rama 429:10
- Shulchan Aruch HaRav 429:15, Kaf HaChaim 429:22, Chazon Ovadyah (pg 3), Mishna Brurah 429:8. However, the Aruch Hashulchan (429:7) writes that on the 13th day of Nissan, one should begin a few pesukim ealier, from "Vezot chanukat" (Bamidbar 7:10)
- Perisha YD 270:7 writes that since nowadays writing down Torah SheBaal Peh is treated as though it’s permitted and that we don’t learn from nuances in the text, one shouldn’t degrade the holiness of a Sefer Torah to learn from it, but rather one should learn from a sefer. Chazon Ovadyah (Pesach pg 4) argues that this is only according to the Shach’s explanation of the Rosh that nowadays there’s no mitzvah to write a Sefer Torah and the primary mitzvah is to write sefarim. However, according to the Bet Yosef’s explanation of the Rosh that even nowadays there’s a mitzvah to write a Sefer Torah, then it seems one may learn from a Sefer Torah and there’s no issue of degrading its holiness. He supports this from the Radvaz 3:529 who recommends reading Shenayim Mikrah from a Sefer Torah. Chazon Ovadyah (pg 3) concludes that the minhag is to read it from a chumash.
- Rama 429:1. Mishna Brurah 429:6 and Shaar Hatziyun 429:10 emphasizes the significance of the obligation.
- Halichot Shlomo (Moadim vol 1, 2:2), since there is no set amount that must be given and it isn't considered a a total obligation.