Quote from Derren on Chris Moyles on Radio 1 (March 4th 2003):

How to play Roulette:
You've got your 3 fields: you've got your top 12, your middle 12 and your bottom 12. So you put your money on any 2 of those ... the ball goes round and you've got a 2 in 1 chance of that coming up, and you will win half of what you put down back again. 1 in every 3 times you will lose twice as much as you put down. So over time it will balance out, but if you do it just a few times you have a good return, so that's they way to play roulette.