3 ways for you to figure this out...
1.) color 3 lugs in a row on a tire with chalk. Drive down the road. The goal is to get the chalk to wear off. If chalk is still on the ends, let a couple pounds out and repeat. Chalk in the middle? You went too far. Add a few pounds.
2.) ask on a forum
3.) just drive it. After a few hundred miles you'll see where it's wearing. Look at my jeep profile. In it I have a pic of my tire tread. Click it and look closely. You'll see how the tread is dirty, but cleaner on the edges of the outside lugs. This is a little too much, but it'll work. As long as your wear is within 1" of the outside, you'll be ok.
Since I read this, I let more air out. I stated above I'm at 28psi on a 2 door on 15" wheels. To get even wear, I aired down to 25psi to get it even across.