My comments in A Small World (a private international travel and lifestyle community) thread about Twitter: Best practices on Twitter seem to be 1) post items of value 2) grow your network organically -- no schemes, no mass following whoever 3) engage with others and react to the material they share. (Be selective and honest about your interests.)
Use Tweetdeck or Seesmic to better organize the feeds you subscribe to, group them meaningfully, and actually build a series of networks that relate to who you are, where you are, what you do, what you want to do, where you want to go, and if you like, where you came from. I add to that all the lives and pursuits I didn't choose but I am nevertheless still interested in. We *can* live vicariously!
I hear what detractors are saying but all their points are disproven on Twitter every day.
It's not the same (or less than) a status post on a FB wall for a slew of reasons -- public search being just one of them. It's untrue you can't say anything impactful in 140 characters, but I agree it takes some getting used to. Tiny urls and succinct introductions are a way to bring substantial value to a Tweet.
If you follow people who use Twitter well, you'll be wowed. And if you use Twitter well, you'll be surprised on a regular basis at who and what it brings into your life.
BTW, I was just at TEDGlobal this week and by using Twitter I not only connected with a ton of attendees I might have missed, convening from all corners of the world, but I also got a richer view of the conference through their tweets --- including how and what they heard the speakers say on stage in real time. TED events are info-overload, and Twitter made it that much more accessible.