Water!!! If you are heading for your stand to sit for a day, take lots of water ... 2 bottles won't last you as long as you think.
Nap. Enjoy that mid-day yawn session, check that yoru safety is on and have a short catnap - there is nothing more satisfying than waking up refreshed in the bush, in your favorite hunting spot, with a gun in your lap. Don't worry about what you may not see ... if it was meant to be, you'll be awake for it. The last thing you want is to be fighting the yawns and blinks and make a bad shot, only to wound the animal.
TP or baby wipes for sure. Especially if you are hunting at a camp "away from home".
Prior to the hunt:
Sight in your rifle at least 3 seperate times! This will tell you for sure if during transport, etc.. if anything is changing (loose scope, etc..)
Make A List of what you want to take with you for the trip - include the most "obvious" of items on your list. We all know that you wouldn't go hunting without your favorite knife, but it's just these kind of "everyday" items that get overlooked when you are busy thinking of the small details.
If you are hunting Dear/bear/moose ... take your latest UnRead hunting magazine to the stand with you every day. When you make your shot, read a few articles. Then read one more. I find this is the only method that keeps me from jumping up and searching for my kill too soon. It's dead, it's not going anywhere - enjoy your time outside while you can.
Again, with larger animals ... if you are sitting on the edge of a brush/swamp waiting for something to emerge from the trees ... Don't shoot the animal when you first see it emerging. Let it have it's drink/snack, then shoot once it has turned to head back to the bush. When you shoot them, they tend to bolt int he direction they are already pointed. The last thing you want is to have them bolt 100 yards into the muskeg. Your patience ahead of time will reward you with a much easier recovery of your kill. If it's a narrow clearing with swampy bits, set yourself so that you can shoot them after they have finished crossing the wet parts in either direction.