(a) Zayin Adar:

On the seventh of Adar (the anniversary both of the birth and of the passing of Moshe Rabbeinu) and at the preceding Minchah, the Rebbeim of Chabad never said Tachanun. This was the case after they had assumed the leadership, never beforehand.1

(b) Purim Laws and Customs of General Application:2

“When Parshas Zachor is read on the Shabbos before Purim, (and likewise when it is read on the Shabbos of Parshas Ki Seitzei [from which it is drawn]), there are varying traditions as to how to pronounce the word זכר, whose first syllable can be vocalized either with a tzeirei or with a segol. The same doubt exists when this word appears in the Torah reading of Purim, (and likewise on the Shabbos of Parshas Beshalach [from which it is drawn]). Here, too, I have not received a specific directive.

“It would appear that in each case the word זכר should be read twice. On Shabbos Zachor (and in Parshas Ki Seitzei) it should first be read with the letter ז vocalized with a tzeirei and then with the letter ז vocalized with a segol. In the Torah reading of Purim (and in Parshas Beshalach) it should also be read twice, but with the vocalization in reverse order.”3

At Shacharis on the Fast of Esther we say Selichos (Siddur, p. 359ff.) and Avinu Malkeinu (p. 277ff.).

The [three] coins of half a shekel (machatzis hashekel) are given [to charity] on the fast day, even when Purim falls on Sunday, [in which case the fast is observed on the preceding Thursday].

In the Megillah written by the Rebbe Maharash, (a) not all the columns begin with the word המלך, (b) nor do the names of the ten sons of Haman (Esther 9:7-9) occupy a separate column.4

Those listening5 to the reading of the Megillah fold their scroll [just as the reader does] like a letter,6 into three parts.

It is customary to “strike Haman” [by means of noise-makers and the like] at the mention of his name, at various stages in the reading (i.e., when he is described by an epithet, such as האגגי — “the descendant of Agag,” or הרע —”the wicked”).7

In the Megillah (8:11) we read להרג ולאבד ולהרג ולאבד, and (in 9:2) we read ואיש לא עמד בפניהם ואיש לא עמד לפניהם.8

The Megillah is rustled at the mention of the words האגרת הזאת (“this letter”; 9:26) and again at אגרת הפורים הזאת השנית (“this second letter of Purim”; 9:29).

We recite the blessing of Shehecheyanu (Siddur, p. 339-340) by day as well [as at night].9

On Purim day the tefillin of Rashi are worn when the Megillah is heard and read.10

The wording in Shoshanas Yaakov (Siddur, p. 340) is: ארורים כל הרשעים ברוכים כל הצדיקים — “Accursed be all the wicked, blessed be all the righteous.”11

Minchah is held earlier that usual and is followed by the seudah, the festive meal of Purim.

The rejoicing of Purim far surpasses that of Yom-Tov.12

The days of Purim13 are days of feasting and joy.14

(c) Customs of the Rebbeim:15

A silk coat is worn, as on Shabbos or Yom-Tov.

Half-shekel coins are given on behalf of the Rebbitzin and for young sons and daughters.

Even in private (i.e., even without a minyan) the blessings before and after the Megillah are recited, both by night and by day.

Mishloach Manos (gifts of food; Esther 9:19), comprising food and drink, are sent to three people.

A sable hat and a gartl are worn for netilas yadayim, the blessing of HaMotzi and the Grace after Meals, and for the maamar.

A maamar is delivered at the festive meal.

It is the custom of the Rebbe Shlita to make an appeal during the farbrengen on Purim.16