First, I have only been using twitter for about 7 months (since 16 April, 2009), and in that time I've made 1,090 tweets, followed 418 accounts, 384 have followed me, and in just over a week (when twitter lists were added) I have been added to 40 lists by other twitter accounts.
My account: http://twitter.com/aqlong
Lists I created: http://twitter.com/aqlong/lists
Lists following me: http://twitter.com/aqlong/lists/memberships
These are not super-huge numbers, but the point is that I'm a consistent user and engage in my community with on-topic tweets, most of which I hope are helpful in some way to at least some of my followers. This creates loyalty so that your twitter followers continue to follow you instead of removing you. If you always think to yourself before you tweet something, "is this interesting or helpful to any of my followers", then you're on the right track. If you simply answer, "What are you doing right now?" all the time, you probably won't be engaging with your community very effectively.
If you look at the links above, there is a clear theme here that my account, my lists, my tweets, my followers & friends are by and large related to one technology: ColdFusion. Focusing on one or two themes is essential in my opinion.
To the success story:
The other day, without much forethought, I sent a tweet from my company BlackBerry via TwitterBerry:
"I'm curious: how many of you #Coldfusion developers out there don't have a job now or know an unemployed CF dev?"
Within minutes, I had a bunch of replies from my followers. This screenshot is via the twitter implementation in Digsby:

As you can see, some people re-tweeted my question (using "RT" plus @aqlong). So, naturally I followed up with: "For unemployed #coldfusion developers: who would be willing to move to another country for the right position?". Quickly I got these responses:

I also got 3 Direct Messages (DMs) regarding those tweets, but since those are meant to be private, I will keep them that way. Next, I sent this tweet: "#ColdFusion developers willing to move to Holland, we have a Junior Web Dev position now: http://digs.by/jwK please RT" <-- notice that I use the hash (#) directly in front of ColdFusion. When clicked on, the ColdFusion link goes to http://search.twitter.com/search?q=%23Coldfusion, which some people interested in ColdFusion use to find out anything & everything interesting about ColdFusion. So, there were a few replies to my tweets that were not even previous twitter followers of me.

Within about 8 hours we had 4 high-quality candidates who applied via our website and began the recruiting process within the Peoplexs system. Interviews begin shortly. ;-)
Aaron Longnion
Director of Internet Technology
www.PeopleXS.com
Join the PeopleXS Community at www.peoplexs.com/communities/nl/
Director of Internet Technology
www.PeopleXS.com
Join the PeopleXS Community at www.peoplexs.com/communities/nl/
