Online Dating Advice?

frankgod asks: "I'm a 25/M/US geek who managed to get through school with my singleness intact. I plan on staying single for a while into the future, but I am considering online dating in addition to other methods of meeting local women for casual dating. Any advice on particular sites and tweaking profiles or search results? I've looked at eHarmony , Lavalife (sparse local results) and Match.com (seems to be best of the bunch.)"