Top Ten Rules to Follow for Tournament Dominance!

1- NEVER allow opponents to take back a move.

2- Don't wash, bathe or otherwise perform any bodily hygiene
   three days before any tournament. This includes brushing
   your teeth, or wiping.

3- When your opponent is out of cards, all lands tapped, fireball 
   him for 10 more than needed and scream "I'll teach you to squeal 
   like a pig!!!". Everyone will look at you in fear after that.

4- Laugh hysterically at the first card your opponent plays, and 
   mumble "I am so lucky to face scrubs all day".

5- If you're losing, call over a judge and ask for a deck check.

6- Learn the systematic and slow way of counting your hand, your
   opponents hand, your graveyard, your opponents graveyard, your
   library, your opponents library, permanents in play, and life
   totals. Don't forget, this process can be repeated many times. 
   Snatching a draw or win from the jaws of defeat takes alot of 
   counting, get good at it. (Strategy tip: If your opponent
   accuses you of stalling, accuse him of being unsportsmanlike.")

7- In constructed events, always play with an all "Black-Border"
   deck, no sleeves.

8- When playing against a 10-years-old kid, who's probably in his 
   first tournament, ask to decide who'll be playing first by 
   arm-wrestling.

9- When you win tell your opponent "It's all about subways", and
   smile. Graciously refuse to explain what you meant if asked.

10- Enjoy playing the game of Magic. Never forget it's a game. 
    Remember every game has winners and losers. If you win remember
    it's because of your superior "skillz". If you lose remember
    it's due to "Dumb scrubby luck".

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With thanks to Manuel Bevand for material and inspiration.