I was trying to setup a WordPressMU site and I needed to enable Wildcard DNS. I found some excellent resources on this at this page run by 1&1 hosting.
http://www.1and1faq.com/forums/archive/index.php/t-602.html
Some of the commands in SSH regarding the websrvmng confused me. The following page shows some of the commands you can run on this program.
addendum:
I setup another WordPresMU site. I had problems using the site even after following the above instructions. The problem turned out to be that the first site DNS info was with Network Solutions who already had a CNAME record with the wildcard domain setup. The new one was being hosted by GoDaddy. This did not have a wildcard for sub-domains setup by default. I tried to setup a CNAME record but it was refused. I created an A name wildcard. That’s doing the trick.