The only tip that I can add to all of the previous comments is to make friends with the national forest ranger staff in the district where you want to camp. Go into the office. Buy some paper maps -- the forest road maps are great (and huge) and often list roads that are not on the computer topos. Talk to the ranger -- find out which areas are off-limits for boondocking (such as near campgrounds). If you are lucky, the ranger will give you some great suggestions. It depends on who is on duty that day, how busy they are, and so forth. Kind of time consuming, but it's part of the fun of hunting for good sites!