This may be personal preference but i stand 80% of the time when i am on stand and sit only 20% of the time. Even on 12 hour sits i do this. Its the old saying "better to be prepared and have nothing happen, then to have something happen and be unprepared". I am much more comfortable taking standing shots than sitting shots. You will not always have a chance to stand, so why not already be standing. Yes this is more tiring to do but it also forces you to stay more alert. Sit only when your feet hurt too bad to stand and you will not be caught in a bad position when the chips are down.
I also feel that it is important to practice on every deer that comes by. What i mean by this is read the deer. Pick the time at which you would draw, pick the lane you would take the shot through and imagine your holding point. This will make it much easier when the moment of truth arrives.