Get your black belt in Twitter
"Even though half the universe is on Twitter these days, beginning out of nothing isn't always that evident. If you really want your Twitter to fly high, it doesn't end with just creating an account. In 40+ pages, this guide from MakeUseOf (May 2010) tackles every Twitter feature, tip and trick you can think of. Learn to work the interface, how to tweet from your desktop, as well as cool Twitter bots and funniest people to follow. This free Twitter guide will get you a black belt in Twitter in no time.
(Some of the sites referred to are no longer active, but the basic information is a good overview for new users.)