It also depends on the size and model of the tire, but 95/105 worked for me on most tires when I weighed 150-160 lb. 100/110 after I ballooned up to 180.

I used to think the higher the better, but that's not true for a variety of reasons. It's actually slower, rougher, and apparently can push more against sharp objects to help them penetrate the casing. You just also don't want to go too low, or you start getting pinch flats.