One mistake that I made this year was in assuming I could thread my way through the woods in the dark to my stand without any markings. There was far too much unnecessary stumbling and crashing through the woods: next year I plan to carefully mark a clear path.
I think this same thing hinders many peoples setups. The more low key you are the more successful your hunts will be.
Although for some marking entry exit routes to their stands can tip off other hunters to their locations. Sometimes you are hiding from other hunters as much as you are bowhunting whitetails.