Shulchan Arukh, Orach Chayim 693/שולחן ערוך·אורח חיים תרצ״ג

1Order of Prayer on Purim. Containing 4 paragraphs: After you read the megillah at Maariv say Ve'atah kadosh and if it falls on Motzi Shabbos say Vayehi Noam prior to Ve'atah Kadosh. Rema: and say Vayitain Licha and say the the Megillah and afterwards Havdalah. (Minahgim)

2Say Al Hanisim during the night and day. Rema: If you didn't say it you don't repeat (Tur) and Al Hanisim is only said on the 14th but not the 15th. (Beis Yosef in the name of A"Ch and Minhagim) On the night of the 14th even though they haven't read the Megillah you say Al hanisim in Maariv. (Hagahot Maimoniyot Ch. 2)

3We don't say Hallel and Tachnun. Rema: We don't say Lamatzeach and El Erech Apayim (Minhagim and Beit Yosef in the name of Tosfos)

4We take out the Torah and we read Veyavo Amalek and even though it has 9 verses, the last verse is read twice in order that 10 verses. Its not the custom to read the last verse twice. Then we read the megillah and afterwards the Kedusha. Rema: If there's a Brit on Purim we circumcise the baby before the Megillah.(Mahril and Minhagim)