Well, if you can stand it, wear briefs or boxer briefs. These are a little tighter and will keep the buldge from standing out. Also, if you get an erection, try drinking something to help get rid of it. If you don't want to wear briefs (they are often called "tighty-whiteys" or "uncool"), then try wearing semi-tight pants (don't wear tight pants, or else your erections will be even more visible.
Or, just wait about 5 years. they'll stop by then.