Keep your log current! (It helps if it's also neat) because that's usually the first thing they want to see - if it looks questionable, they'll look harder at everything else. All paperwork, such as permits, & personal documentation, like the long form medical certificate, accessible. Shipping papers at hand if under load, & safety equipment present & in good order.
Again: keeping your log current & legible is a big help. I've been caught by surprise twice - once at a scale, & once on a Pennsylvania back road, and both times I was glad that I'd kept my log up! (Because there have been times when I didn't)
A clean truck helps. Stay on top of air leaks and keep your brakes adjusted. If they're standing outside looking you over as you approach you will have a good chance of just getting the quick once over and avoiding a level 1(or whatever # the major inspection is).
Look professional, act professional.......be precieved as a professional. A nice clean appearance (driver and truck), all records (logs, permits, etc) readily accessable and the level of inspection will probably stay at a 1, as stated before, neat, up to date logs is the first indicator of how the Officer precieves your professionalism. Remember, perception is reality!