Ideally, Megillah should be read after sunrise (5:36am). Shacharit should be timed to read the Megillah as soon as possible. In extenuating circumstances, one may read the Megillah after dawn (4:23am).
Ideally, men should not eat before hearing the Megillah. If this is difficult, or there is any concern that one will be unable to concentrate during davening, one may snack, but should not eat a K’beitzah (57 grams) of Mezonot. Nevertheless, one should not be stringent if there are any health concerns.
Al Hanissim is recited in the Amidah, and Tachnun is not recited.
If one did not hear Parshat Zachor on Shabbat, he should have in mind to fulfil his obligation through the Kriat Hatorah of Purim. [For this reason, the Ba’al Koreh should intend to be Motzeh anyone who did not hear Parshat Zachor on Shabbat.]
During Kriat Hatorah, the word זכר is first read with a Segol - זֶכֶר, then again with a Tzeirei – זֵכֶר. Some repeat just the word, some repeat the phrase תִּמְחֶה אֶת זֶ כֶר עֲמָלֵק whilst others repeat the whole Passuk. (the reverse of Parshat Zachor).
Some hold the Sefer Torah is returned to the Aron Hakodesh and some including Chabad hold that the Sefer Torah remains out during the Megillah reading, and is returned only after Kaddish Titkabel, as usual. [The one who holds the Sefer Torah remains seated throughout the Megillah reading and associated Brachot.]
If one did not yet give Machatzit Hashekel, he should do so before the Megillah reading.
When the Brachah of Shehecheyanu is recited, all should have in mind the other Mitzvot of Purim; i.e. Mishloach Manot, Matanot Lo’evyonim and Seudat Purim. [Preferably, the Gabbai or Ba’al Koreh should announce this.]
One should wear his Tefillin until after the Megillah reading (and davening).
