Congrats my man. I'm all about drinking responsibly. I'm also a realist. So with that in mind, I will give you a few tips if you plan to do the moronic thing (like I did) and take 21 shots.
Rule 1: Eat, eat, eat. Eat as much as you can.
rule 2: Don't drink anything but shots. Don't add any more alcohol to the equation.
rule 3: Start taking the shots early in the day. 21 won't seem so daunting if you go into dinner already having 8 shots down that have been spread out over the previous 6 hours.
rule 4: have 2 really good friends. one to buy you low alcohol or "girlie" shots. the other to be sober and be there to tel you to stop if you need to.
rule 5: have a friend hide your keys and not let know the location until tomorrow when you sober up
So, don't do it. But if you do, follow these rules and your chances of looking like a fool will drop dramatically.