I would recommend a trip to your local shooting club on a NRA highpower or F-Class leauge. Talk to the guys local to you, and find someone in your area. Usually the guys shooting competition will sort out the hacks from the good ones in a hurry.
Other than that, start thinking about what weight bullets you want to be shooting. Pick a twist that will maximize the potential in the bullet range you are looking at. Another thing, if you want to shoot the really heavy bullets you may have to short throat the chamber to get your loaded rounds to fit into the mag box.
