I found some great information by Jaime (last name unknown) on her blog, She's Baty Designs, about using Twitter, so I thought I would share. This advice looks good whether you are a newbie, or someone who currently uses Twitter.
1. Follow your followers! this is the best way to make sure you don't lose any people who start following you.
2. I use "twitter karma" to find out who's not following me so I can unfollow them. You'll find this REALLY helpful to deal with people who follow you only until you follow them back (and then they unfollow you right away - not cool!). Once you see who's not following you, just click on their name to manually unfollow them. I use twitter karma every few weeks (or when I can't follow anymore people) to clean up my account (and keep my twitter account growing). Here's the link:
3. On buzzom.com, you can bulk unfollow people who are no longer following you. You can only unfollow 25 at time but just keep clicking "more" until there isn't any more... then click "flush" again and you'll get the rest of the people who aren't following you. Here's the link: http://www.buzzom.com
4. I use twitterfeed.com so all my new Etsy listings get tweeted. I also use it for new flickr uploads :) Be sure to add hash tags when setting up these feeds. For example, on my Etsy feed I have #etsy added to the end of every Etsy tweet. This will help people find me when they search hash tags on twitter. Here's a helpful link for hash tags: http://hashtags.org/
5. To find people to follow in your target audience, check out the lists people have already made. Lists are groups of people that someone has collected because these people tweet about certain things - Etsy for example. You'll find these lists on the right side of people's twitter profiles. Go to the profile of someone you are following (or check out etsy's twitter profile) and look for "etsy", "crafty" or "handmade" lists. You'll find lots of great Etsians to follow on these types of lists. I'm in a lot of Etsy, crafty and handmade lists so you can also check out my profile to get you started: http://twitter.com/shesbatty
6. To set up tweets to post later (when you're not going to be at the computer for example), use hootsuite.com. I've found this to be the most useful site for "tweeting later". This is a great way to set up a bunch of tweets at once without bombarding your followers. It's also a great way to get some tweets out there during times that you wouldn't normally be at the computer so you're reaching the most amount of people.
7. Make sure you set up your twitter profile completely. Have an avatar! I usually won't follow anyone that doesn't have an avatar (that icon that shows up when you tweet). 9 times out of 10 if the person doesn't have an avatar (and just has the twitter bird as their picture) they are a spammer and/or questionable. Be sure to add your Etsy or blog link to your profile and write a little bit about yourself. It's also helpful to include your location (State/Province and Country is usually sufficient) and "Etsy" in the "name" section of your profile. For example "She's Batty on Etsy". This will help people find you when they are making groups or lists (especially if they are using TweetDeck - the app I use to make using twitter WAY easier).
8. Don't spam with auto DM's (direct messages)! This is one of the fastest ways to get yourself unfollowed.
9. Don't just post links to your "stuff". If you're only going to take about yourself, soon you'll only BE talking to yourself!
10. Retweet interesting and helpful posts from other people.
11. Interact with other tweeters - reply to their messages, ask them questions, congratulate them on sales, etc.
12. Aim to tweet at least every few hours (but NOT every few minutes - don't overwhelm the system with a million tweets per minute!).
13. Keep your tweets interesting. Vary from links, to questions, to observations, to "regular" stuff. Share all your fav finds on the web and try to be as helpful as possible. But try to keep links to a minimum so you don't get reported for spamming (you can do this easily but offsetting link tweets with another non-link tweet).
14. It's OK to block "questionable" followers. This will mean different things to different people, just go with your gut.