Absolute 100% FOOL PROOF way you will win your Promos.

Step 1: Get to promos Step 2: Start playing normal games. Throw every game. And I mean feed, every lane, make sure your team loses. Go AP Talon or Kassadin adc or something. Step 3: Repeat step 2 like 10 times. Or more. The more the better. Step 4: Play your promo games. Now that you've lost 10+ games in a row, statistically you HAVE to win the next 10 or so, to maintain your ~50% (or whatever you had) win ratio.

You're welcome.