1-stick to one account, and make it obvious that it is run by a human. You are you, the books, blogs, whatever you sell and do, etc are a part of you. You'll go nuts trying to follow the same people with 10 different accounts, and it won't be as effective. If it builds and you get a feel for it, add more as needed, but you are the brand, the rest are products.
2-fill out your profile completely, especially the website.
3-When you follow someone, try to make it look like you have a reason to. Reply to something they tweeted that is of interest. Ask questions. ENGAGE.
4-Unless they're spam or totally useless, follow people back. Receive email notification of anyone following you so you can reciprocate.
5-interact creatively. As questions. You are actually building relationships with people. Meet as many of them in person as possible. That means following local people and attending and or hosting events they will be at. Everyone loves fundraisers for a local charity. http://twilightYEG.ZoomJer.com
6-Remember that it is just another way to network with people, and if you follow people who might one day be your clients, the business will follow.
7-tweet about your business/expertise/interests and people will see you as the expert and ask questions.
8-use twitpic.com. It is built into many twitter applications so that you can tweet and upload a photo in one shot. Twitpic allows you to see how many times a photo has been viewed, which helps to know what people find interesting. http://twitpic.com/photos/zoomjer
9-shorten links with http://kl.am. You need the space in your tweets, plus you can also see how many people clicked on it (create an account).
10-Be diligent. Once you build momentum, you will start to prefer @replies more than email!
You know I could go on about this for far more than 10 suggestions, so why not add your own?
Here's a link to a live online presentation I did, plus a website explaining how I use Twitter and facebook for business: http://tweetup.ZoomJer.com/