#4: Build Relationships, Don't Advertise
Twitter is a conversation tool, not a broadcasting tool. It's not a place for you to put out "buy my stuff!" messages over and over. While it's okay to put out messages about you once in a while, they should be kept to a minimumabout a 9:1 ratio. That is, for every nine messages you put out about someone else, one can be about you.
It's the basic idea of Giver's Gain. Do stuff for other people, because it will do you good in the long run. Retweet other people's good stuff, like their blog posts, their announcements, and their victories. Then, the people you did it for will return the favor. But, so will other people who watched you do it. (That's where Giver's Gain really takes hold.)