I think a better new member interface could help. These are just a few of my ideas, YMMV:

*If a new member wants to start a thread a screen could come up directing them to perform a search before the system allows the new thread to be created.

*There could be a waiting period before new members are allowed to start a thread.

*New threads, maybe the first 10 that new members start could require approval by the mods before they apprear. I know this would be adding an additional burden on the mods, but it could really cut down on some of the trolling.