Columns don’t contain consecutive numbers – for example, the first column has 1, 4, 7, 10, 13, 16, 19, 22, 25, 28, and 31 – and the number of red and black numbers differs between each column, a fact that we’ll cover in a moment. And remember, the 0 and 00 aren’t included in any of the columns because they’re special and too good for all the other numbers.
Bet on the inside in moderation to increase your payout. Though they have the highest payout, straight bets on a single number are risky. The odds of the ball landing on the exact number you chose is 1 in 37 (2.7%) for European wheels and 1 in 38 (2.63%) for American wheels. In addition to making a straight bet on a single number, you can also divide the odds between multiple numbers.[3]
In other games the color of the chip denotes the denomination, but in Roulette the color denotes only which player the chip belongs to.  Roulette chips can in fact be any denomination—\$1, \$5, \$25, etc.  When you buy in, tell the dealer what denomination you want. He'll put a marker on his stack of chips that are the same color to note how much each of your chips is worth.  Because roulette chips are non-denominational, you can't use them in other table games.  When you're done playing roulette, give your chips to the dealer and she'll exchange them for regular, denominational chips.
Make outside bets for better odds of winning. As long as you make the table minimum for each individual bet, you can make multiple outside bets to increase your odds of a payout. For instance, if you wager \$1 on even and \$1 on black, you’ll win a \$2 payout if the ball lands on black 10, and you’ll break even if it lands on red 16. Along with even/odd and red/black, which offer payouts of 1:1, outside bets include:[2]
Even if there isn't a betting limit, and if you have an infinite credit limit, it still doesn't really work, it just doesn't really fail either. If the martingale strategy is continued indefinitely and without regard to betting limits, your bankroll will hit arbitrarily high positive and negative values. The expected value is still negative, but the variation is so high that it your bankroll won't stay either negative or positive.