The Havdalah service marks the end of Shabbat. It should be performed no earlier than nightfall on Saturday night. Nightfall is the time when three stars can be seen in the sky. It is normally about 45 minutes to an hour after sundown, depending on your latitude. For the precise time when Shabbat ends in your area, consult the list of candle lighting times provided by the Orthodox Union.
You will need three things for this ritual: a glass of wine or other liquid, some fragrant spices, and a special Havdalah candle. (jewfaq.org)