Even better: Every thirty seconds you get a pop-up that says some things like:

"Use the search button"

"Use the search button, dumbass!"

"I DON'T SEE YOU SEARCHING, YOU PIECE OF DIRT!"

"YOU THINK YOU'RE TOUGH, YOU THINK THAT YOU CAN JUST POST A NEW THREAD WITHOUT SEARCHING FIRST? COME ON, TOUGH GUY, LETS TAKE THIS OUTSIDE!!"
That would be awesome!
p.s. I like the flashing search button idea too. Actually, maybe a small message above the subject area for when you're creating a new thread would be helpful. Not so extreme as my messages above, maybe just "
What you're going to talk about might already be being discussed! Click here to find it."