Studying hilchot Pesach: Thirty days before Pesach we start studying hilchot Pesach. It is a daily obligation to carefully review hilchot Pesach during this period. One should also start cleaning the house and buying necessities for Pesach. Many pious individuals start these preparations exactly thirty days before Pesach, which is the fourteenth of Adar — Purim.
Even a person who studied hilchot Pesach in previous years should relearn them, since it is common to forget various details. Another reason to revise them is that by studying a halachot, one creates an angel that will guard him from transgressing it.
The obligation to study hilchot Pesach is incumbent on the public as a whole, not just on every person individually. However, this does not mean that groups who learn Torah regularly must devote all their time to studying hilchot Pesach, it is enough to dedicate a small amount of time daily.
Tachanun in the month of Nissan: Tachanun is not said during the entire month, since most of the month is auspicious, as mentioned above.
“Tzidkat’cha” is not said during Minchah on Shabbat. This is the principle throughout the year; on dates and occasions when we do not say Tachanun on weekdays, we do not say Tzidkat’cha on Shabbat.
Sephardim do not say Lamnatzei’ach ya’ancha nor T’fila l’david in Shacharit throughout the whole month. Ashkenazim do say Lamnatzei’ach ya’ancha during this month, but not during Pesach nor the day before Pesach.
Parshat Han’si’im: The mishkan was erected on Rosh Chodesh Nissan, and the n’si’im of the tribes of Israel offered up sacrifices at its dedication. For the first twelve days of the month, a different tribe would sacrifice each day; therefore, it is our custom to read the description of these sacrifices, each on its appropriate day, from Rosh Chodesh Nissan onwards. On the thirteenth of Nissan we read about the lighting of the menorah which was granted to the tribe of Levi in place of a sacrifice.
After the reading of these sacrifices, it is the custom to recite the “Y’hi ratzon” on behalf of the deceased, as is printed in the Siddur. The Ben Ish Chai would say this prayer during the entire month of Nissan.
There are some who read the portion of these sacrifices from a Sefer Torah, but the proper custom is to read them from a siddur or chumash.
Fasting during the month of Nissan: We do not fast during the month of Nissan, even on a “yahrzeit”, accordingly a groom and bride need not fast on their wedding day. The Mishnah B’rurah, however, is of the opinion that a groom and bride do fast, even on Rosh Chodesh Nissan.
We do not proclaim a public fast during the month of Nissan. One who had a bad dream is permitted to annul it by fasting. The firstborn son fasts on the Eve of Pesach.
For those who fast on the eve of every Rosh Chodesh, some authorities rule that they must not fast on the eve of Rosh Chodesh Iyar, since it is still the month of Nissan, They should fast after Rosh Chodesh Iyar instead. The Ben Ish Chai however, permits one who wishes to fast or has observed this fast until now to fast on the eve of Rosh Chodesh Iyar.
Mourning and visiting a cemetery: We do not say Tziduk hadin during the seven days of mourning, even if the deceased was a great Talmid Chacham. However, places that have the custom to say Tziduk hadin even during the month of Nissan may do so.
We do not deliver eulogies during the entire month of Nissan, except for a Talmid Chacham at his funeral before burial.
The custom is not to visit a cemetery during the month of Nissan, one who has a yahrzeit during this month should visit the grave on the day before Rosh Chodesh Nissan. However, at the conclusion of the shiv’a or the sh’loshim, is permitted to visit the grave.
The custom is to visit the cemetery on the day before Rosh Chodesh Nissan, to pray profusely for the spiritual welfare of the deceased, since the Zohar explains that there is special benefit to the deceased from Mitzvot and good deeds that are done on their behalf during this month. It is recommended to do so on the eve of Rosh Chodesh Iyar, as well.
Kimcha D’Pischa: The Zohar writes that a person should rejoice and gladden the hearts of the poor on every Chag and at every opportunity, and concerning somebody who cares only for his own happiness it is written “I (Hashem) will throw on your faces the excrement of your holidays,” and “My (Hashem’s) soul hates your Rosh Chodesh and holidays, they are burden to me.” Therefore a person should be solicitous to cheer the hearts of the poor, orphans, and widows, and in recompense Hashem will gladden the person’s heart.
The Rambam writes that it is a mitzvah to rejoice and gladden one's wife and children, and continues: “When he eats and drinks, he is obligated to feed the convert, orphan and widow, as well as the poor and unfortunates. However, he who locks his doors and eats and drinks with his family and does not provide food and drink for the poor and troubled, this is not “rejoicing in a mitzvah” but rather “happiness of his belly,” and about people like this it is said “Their sacrifices are akin to robbed bread, all who eat it become defiled, let them keep it for themselves.” Such revelry is only dishonor, as it says, “I (Hashem) will throw on your faces the excrement of your holidays.”
It is an age-old custom to distribute wheat to the poor, in order to help them with the many expenses of the Chag. In current times we donate money to organizations that distribute food to the needy.
It should be emphasized, that there are authorities who consider this custom an obligation on every person, and not a mere “chumra” (optional stringency) or “chasidut” (beyond the letter of the law). Therefore, anyone who has lived in his present city for at least thirty days is obligated to donate to this cause. Similarly, a needy individual who has lived in the city for at least thirty days is entitled to receive from this charity. The charity is distributed according to need and size of the family.
Shabbat Hagadol: The Shabbat preceding Pesach is called “Shabbat Hagadol.” It is the custom to orate on this Shabbat, both as concerns the laws of Pesach and the themes of the Chag, in order that the public will know the proper way to observe the Chag. One of the reasons it is called “Shabbat Hagadol” is because a grand audience comes to hear important laws.
The purpose of the oration on Shabbat Hagadol is in order to instruct the populace what to do, which is largely preparations before the holiday itself. Consequently, when Pesach falls on Motza’ei Shabbat it is the custom to orate on the previous Shabbat, in order that the congregation will understand how to make the preparations during the ensuing week.
The Sephardim do not make any changes on Shabbat Hagadol in the liturgy or the meals — everything is as a regular Shabbat. Ashkenazim read an excerpt from the Haggadah, from Avadim hayinu until L’chapeir al kol avonoteinu during Minchah on the Shabbat.
Some congregations read a special Haftarah on Shabbat Hagadol. Most Sephardim read this special Haftarah only when Shabbat Hagadol is the eve of Pesach.
The Ashkenazim do not say during Arvit after Shabbat Hagadol the prayers Vihi no’am and V’attah kadosh after the Amidah. The custom of the Sephardim is to say them as with every Arvit of Motza’ei Shabbat.