On Purim we recite the Al Hanisim liturgy in the Amidah (silent prayer) for evening morning and afternoon, as well as in the grace after meals. In the morning service there is a special reading from the Torah scroll in the synagogue.
THE FAST OF ESTHER
To commemorate the day of prayer and fasting which the Jews held before their victory, we fast on the day before Purim, from approximately three hours before sunrise until 40 minutes after sunset. This day is called "Ta'anit Esther", the fast of Esther.
During the time of the Beit Hamikdash, every Jew was obligated to give a half shekel coin once a year in order to participate in the communal sacrifices. From the first of Nissan, the sacrifices bought from the new monies. Thirty days before, the people were publicly reminded to bring their coin to the treasurers appointed in each settlement and district. The half Shekel coin gave everyone an equal share in the sacrifices. Today, we no longer have the Beit Hamikdash or its sacrifices, but we read the portion of the Shekalim in the Torah (Shmot 30:11-16). It is also a tradition on Purim to give 3 half dollar coins to charity.
On the Shabbat before Purim, we take out two Sifrei Torah. We read the weekly portion in the first and Parashat Zachor in the second:
"Remember what Amalek did to you..." (Devarim 25:17-19).
What is the connection between erasing the memory of Amalek and Purim?
The wicked Haman, who intended to destroy all the Jews in one day and claim their spoils, was the descendant of Agag who was the king of Amalek in the time of King Shaul. Thus we know that Hamman was an Amalekite. This is why our sages ordained carrying out the commandment of remembering to erase the memory of Amalek before Purim. "Remember... do not forget!" .