Keep your keyword blacklist up-to-date! "Request abuse update from centralized blacklist" over and over until you only get one response that is "Not necessary! (Already handled)". Make this a habit! Each time you blog or check out your hitlog or just happen to think about your blog go in and get the latest update.
Clean up your hitlog table! Getting the update doesn't clean out the junk in your hitlog table - it only stops new junk. To clean up you can either click the ban symbol next to each domain name on your stats tab, or, if it's really bad, go to the summary sub-tab and remove a day's worth of entries at a time. This is pretty good for new players who just realized they're covered with icky spammers.
Report new spammers! Always always always do step one, then go ahead and report new spammers whenever they hit you. Click the ban symbol, then click the button for "Perform selected actions". Review the selected actions first, but for sure report them to us so we can figure out if we need to add them or not.
That's pretty much it. You can do all sorts of groovy hacks if you're into it. In fact we even have a forum for [url=http://forums.b2evolution.net/viewforum.php?f=30]Fighting Spam![/url], but you don't need to do that stuff. Just keep your table up to date, dump the junk that's in there, and report spammers who hit you.