I clean my tack and give my horse a bath. I also lunge my horse for 10 min to see if he has any bucks in him that he needs to get out. I also brush him off and use dream coat. You want to make sure your horse is sound and everything fits him a week in advance.
Clean my gear, wash horse (braid if I need to), stable the horse the night before the comp and I don’t ride the day before the comp either. I also make sure at least a week beforehand that my horse is sound and my gear fits.