Here's a step by step for Leopard and it's relatively easy as long as you don't have a .local domain extension.
http://www.smallbizserver.net/Articles/tabid/266/articleType/ArticleView/ArticleID/234/PageID/359/Default.aspxthe .local extension is used for the local machine's Bonjour address. If you do have a .local address you need to disable Bonjour on the machine before it will properly bind to active directory. From the terminal:
Disable:
sudo launchctl unload -w /System/Library/LaunchDaem
ons/com.ap
ple.mDNSRe
sponder.pl
ist
Enable:
sudo launchctl load -w /System/Library/LaunchDaem
ons/com.ap
ple.mDNSRe
sponder.pl
ist