A well-known betting system in roulette is the Martingale system. There are a great number of variations of it. The principle is following: when you win, you pocket your bet. If you lose, you should double your previous bet.By doing this in case you win, you get back your previous loss and one more unit.And so on.
The Martingale System works great only in case you have an infinite bankroll and no betting limits.
Another popular roulette system is the d'Alembert system. This system assumes that after a win, a player is less likely to win again.So after a win, you subtract a chip from your bet. The d'Alembert system also assumes that you are less likely to lose after a losing spin, so in that case, you add a chip to your bet. The fact that the roulette wheel has no memory and each spin is an independent trial with exactly the same odds of a win or loss is the previous spin is a weak point of the system.

Among all the casino games roulette is classic. Roulette is an obligatory element, along with blackjack and craps,in any full service casino in the United States, but in France it's much more popular as roulette is a cultural and historical part of the gambling scene. In Europe people have been playing roulette since the 18th century and nowadays online roulette games are popular all over the world.Modern roulette has been around since at least 1796, when the game was played in Paris in almost exactly the same form it's played today. Roulette comes from multiple other games. In the early 18th century in France was popular "biribi" - an italian ball game which was combined with another wheel game where colors, not numbers were used. The English game "Roly-poly" which consisted of black and white slots was launched in 1720. Thus, roulette is a hybrid of both birib and Roly-poly.To understand a game is to enjoy it.Only in case you understand game you can enjoy it. And although knowledge of the game won't change your strategy or your chances of winning, it will increase the amount of pleasure you take away from the tables.

One subject that always comes up when people discuss winning at roulette or getting an edge is biased roulette wheels. To really find a bias in a wheel, you'd need to clock at least 4000 spins and realistically speaking, you won't find a bias towards red or black. At best you'll find a bias toward a specific set of numbers.
Casinos don't want a biased wheel, because the house edge at roulette relies on the odds being 37 to 1. If certain individual numbers pay out more often than they should, the casino loses money. Casinos don't really have an interest in fixing any of their games since the house edge is in their favor on all of them. If you are able to find a biased wheel, you should bet individual numbers as much as you can. If you're in a rare situation where you have an advantage over the casino, you don't want to waste it on bets with low payouts.
Something related to wheel bias but that isn't exactly the same thing is dealer signature. Some roulette dealers have been spinning the ball for so long that they do it in exactly the same manner and at exactly the same speed every time. This produces a situation where some numbers might come up more often than other numbers.
Usually if you're looking for this type of advantage play it's best to find an older dealer who looks really bored, like they've been doing this a long time. You don't want someone who's really young and just learning how to spin the wheel. You want someone who's spun it so many times that it's become automatic and predictable.
Since it would take about 4000 spins to determine with any degree of certainty any patterns on a roulette wheel, it would take a considerable amount of time to track that many spins. You might be better off learning to count cards or play poker really well instead of trying to get an advantage finding a biased wheel or a dealer with a signature.

Some casinos have special rules.
In Prison/En prison
In case the ball stops at zero slot, the croupier will not collect red/black, odd/even and first half/last half bets, they will stay on the table - in other words they are in prison. In the next spin the players have a chance of winning their original bet back - if their bet wins they will get their original bet back but with no additional win. If it's zero again the bets remain in prison one more time and so on. In prison rule is a considerable advantage for players because the house edge is reduced to 1.35 percent.
La Partage
In case the ball stops at zero slot, the croupier will not fully collect red/black, odd/even and first half/last half bets. The croupier will collect only a half of player's bets and will return the rest to the players. La Partage rule reduces the casinos edge to 1.35 percent as well as In Prison rule.

The Martingale is the best-known roulette betting system. There are a lot of variations of it. You should follow such principle: if you win, then pocket your bet. But when you lose, you double the size of your previous bet.By doing this in case you win, you get back your previous loss and one more unit.And so on.
The Martingale System works great only in case you have an infinite bankroll and no betting limits.