Halachot of Taanit Ester
1) The fast begins at dawn and ends at nightfall
2) No eating or drinking is permitted
3) Pregnant and nursing women are exempt from the fast as are modestly ill people. If one is otherwise healthy but feeling unwell consult your local Orthodox Rabbi.
4) If the 13th falls out on Shabbat we do not fast, due to the honor of Shabbat. We would move the fast to Thursday the 11th.
5) It is customary to extend the fast till after the megillah reading.
6) During the Amidah prayer of the afternoon - Minchah prayer, those who are fasting add the paragraph Aneinu in the Shema Koleinu blessing.
7) The Torah reading of Vayechal Moshe is added.