I like Twitter, but like so many other people, it wasn't really clear to me how to really use it without seeming like a spammer. I have read on a couple of good blogs that I follow to use Twitter as if you were at an affiliate marketing convention, or at a cocktail party. They advised to get in there and mingle. Share your interests with others, and ask questions.
I have found that a great way to communicate with others via Twitter is to ask questions. People are always willing to give their opinions.
Carmen