Here’s a short summary of the mitzvot (and minhagim) of Purim:
1. Monday is the Fast of Esther
2. Mitzvah: Monday night and Tuesday, we hear the Megillah read
3. It’s customary, before the reading of the Megillah at night, to doante the “half shekel”. They’ll usually have actual silver coins in shul. You donate some money, and lift up the coins. The Ashkenazic custom is to use 3 “half shekels”.
4. Mitzvah: festive meal on Tuesday (including lots of alchohol!)
5. Mitzvah: Mishloach Manot – give 2 kinds of food to 1 person on Tuesday
6. Mitzvah: Matanot L’evyonim – give money to 2 poor people on Tuesday
7. Add Al Hanisim to your Amidah and Bircat Hamazon