The biggest bucks I've ever seen excluding the rut have been in dark, swampy, thick cover. I found giant rubs in another swamp area that was very difficult to get into. A large mature buck will stay very close to his "core" area until the rut. He will return to this area again after the rut. The most important thing you can do in my opinion, is to learn the entire area you will be hunting. Get topo maps, aerial maps, and wear out them boots!