Ok, I got this diea off of Yahoo! Answers. When you are posting a new thread, after you finish, or before you start, a little box pops up that shows similar threads, that when you click on the link, it pops up in a new window, so you can search and see if it was already posted, and if it wasn't then you post it. And you can use your User Warning System, to give whoever ignores the pop up points.
Please don't eat me alive if you have already tried this.