It's also important not to sell or promote too hard on your twitter profile. You are talking to real people, so it will pay off to show the human site of your company. Post pictures on twitpic, tweet about your charity involvement and about your latest office redecoration. Or tweet about something in the news that caught your attention.

Thanks for all the responses. Very useful.

If I'll need to retweet other people's posts, I'll need to find some people to follow. How do I find good twits (tweeters?). I've tried researching the competition and the people that follow them, but they are not very interesting.

You can find interesting twitters by searching on twitter for your keywords. For instance, if your company offers search marketing as a service, you can search twitter for "search marketing", and go through all the profiles until you find a few that are interesting.

Another good way to find people that you share interests with is trying the Twitter Packs wiki. They organize twitters by subject matter, region, company, etc.

Another good one is Tweetscan. Here you can search for topics, people, places, etc.

Here's some twitters your should follow, you'll learn a lot from them:

@wholefoods: they bring value by sharing neat things in your community
@jetblue: they give helpful travel tips
@TheHomeDepot: they show you how to promote your employees' or your stories outside of work
Have a couple of employees set up their own twitter account and share interesting stuff. Examples in case are @RichardAtDell, @LionelAtDell and @MattCutts
Talk about more than your business. Mzinga's @astrout and @jstorej do this well.

What a great idea. I never thought of using Twitter to spark communication or to get feedback. I've always thought of Twitter as mainly one-sided communication.