Twitter etiquette; The social decorum expected of you when you join twitter. Examples of good twitterquette:
-- People you know in real life who follow you also expect to be followed.
-- Tweet no more than once an hour (not including @replies), but no less than once a day.
-- Avoid more than 3 tweets in a row, unless directly related to each other and especially important or hilarious in nature.
-- Do not abuse your right to post links in a tweet, especially when the link is connected to shameless self-promotion.
-- Always cite real-life friends on #FollowFriday
-- Although one is capable of a 140 character tweet, using less than 100 characters is ideal.
-- Twitter is not a chat room, no @reply conversations. This can be as irritating as spam.

Keep in mind that these guidelines are taken very seriously in the twitter community.