Hearing the entire megillah from a kosher scroll twice: Once in the evening and once in the morning.
It’s a mitzvah to rejoice on Purim we party and we are also meant to make others happy as well. The Chafetz Chaim (Biur Halacha 695:2 s.v. Chayav and Ad) asks: How can Chazal obligate us to drink on Purim if we find incidents in Tanach (e.g. Noach, Lot, Nadav and Avihu) that demonstrate the great dangers inherent in imbibing alcoholic beverages? He answers (citing the Eliyahu Rabbah) that the miracle of Purim came about to a great extent due to parties where alcohol played a central role. Thus, we consume alcohol on Purim in order to remember the great miracle brought about by alcohol. Biur Halacha also cites an important comment of the Meiri on this issue. He writes: Nevertheless, we are not obligated to become inebriated and degrade ourselves due to our joy. We are not obligated to engage in a Simcha of frivolity and foolishness. Rather it should lead to a Simcha of enjoyment, which should lead to love of Hashem and thankfulness for the miracles He has performed for us.
Rambam writes (Hilchot Purim Chapter 2): "A person is obligated to send two portions of meat, two other cooked dishes, or two other foods to a friend, as implied by Esther 9:22, "sending portions of food one to another" - i.e., two portions to one friend. Whoever sends portions to many friends is praiseworthy. If one does not have the means to send presents of food to a friend, one should exchange one's meal with him, each one sending the other what they had prepared for the Purim feast and in this way fulfill the mitzvah of sending presents of food to one's friends.
One is obligated to distribute charity to the poor on the day of Purim. At the very least, to give each of two poor people one present, be it money, cooked dishes, or other foods, as implied by Esther 9:22 "gifts to the poor" - i.e. two gifts to two poor people. We should not be discriminating in selecting the recipients of these Purim gifts. Instead, one should give to whomever stretches out his hand. Money given to be distributed on Purim should not be used for other charitable purposes.
It is preferable for a person to be more liberal with his donations to the poor than to be lavish in his preparation of the Purim feast or in sending portions to his friends. For there is no greater and more splendid happiness than to gladden the hearts of the poor, the orphans, the widows, and the converts.
One who brings happiness to the hearts of these unfortunate individuals resembles the Divine Presence, which Isaiah 57:15 describes as having the tendency "to revive the spirit of the lowly and to revive those with broken hearts."
We should all learn from here a general rule for life: Don’t Forget to Make Others Happy as Well