Step 9: Fireman's belay
Special thanks to gmoon for reminding me about this one:
A good practice (especially on your first few rappels) would be to have a buddy/belayer use a "fireman's belay" at the bottom. Basically what they will do is hold the rope loosely as you are coming down, and should something happen to you (you pass out, freak out, get knocked out, etc.), they will pull straight down, (taking out all the slack between them and the ATC), which will break for you until you can regain control. If you are incapacitated and they are experienced, they can also adjust the angle at which the rope is held, slowly letting you down, which makes this method superior to other backup methods because your buddy/belayer can let you down, rather than having you stuck there dieing from suspension trauma.