To Change your username, Log in to Twitter > Choose Settings > Username. Type your new username. If the name is already in use by somebody else, you are out of luck. If the name you want has been deleted or abandoned, however, you might be lucky enough to score it.
How did I get the name @kim? When I signed up for Twitter, the name I wanted was unavailable. Yet, I noticed after a while that a lot of people sign up for Twitter, grab the good names only to decide the service is confusing and then flee in terror. At least I assume that’s what happened to whoever initially set up the @kim username. In December 08, I noticed the @kim account still didn’t have any friends or followers so I began petitioning Twitter by filing support tickets.
In the past, there was a six-month waiting period after an account has gone inactive (tweets have completely stopped). Essentially Twitter would hold onto the accounts, hoping users would change their mind and start using the service again. This policy has been vague, but apparently Twitter plans to form some kind of stampede on the good names in the near future. I would love to see this spelled out more clearly, because I get asked the question a lot. Meanwhile, if you’re looking for a name change, keep a close watch for developments!
Sooooo. The best I can tell right now, if you want a username that is being occupied, but not actively used, file a ticket with Twitter support http://help.twitter.com —or sign up for notifications through Twitter Counter (see Next Web for instructions).
Oh, and if you’re superstitious, I find it helps to summon the ghost of Elizabeth Montgomery. *nose wiggle*
Just don’t call me Cher, @Armano, or Prince. I don’t wanna get sued. ;-)