Before you start looking for winning strategies, you need to understand one cardinal truth. The past has no influence on future. There is no 100% successful strategy for winning roulette or any other casino game.
Many casinos offer a pre printed card with all the numbers printed on it for the bettors to keep a track of what numbers have been hit and what have not. This strategy never works. If it did work, the casino will ban players from doing it. So, if the casinos are lending you a helping hand, there is something fishy about it.
Still, there are some basic underlying principles which can amount to strategies. First, play a European roulette, which has only one zero and only 37 slots. The American roulette has an extra 00, totalling to 38 slots. This gives the advantage to the house. So play European roulette to get better advantage.
Never bet all over the table on all numbers. You may win, but this money will be very less compared to what you would have betted. Playing online means, the mechanical wear and tear of the roulette wheel to favour a particular set of number is reduced. Gives you a fair game and you can learn and test strategies for free with free online roulette websites.
In online roulette, you get bonuses. This is not part of real life casino. That adds advantage to you. While placing bets, decide on certain amount you can afford to lose. Let say a $ 500 or £ 250. Start playing by betting 10% of what you decided to lose which is $50 or £25. Stop playing when you have reached half of what you thought you will lose that is $300 or £125. Playing for bets that give you half the advantage like black/red, odd/even, high/low.
This is a famous strategy and wins decent payments. Place 1 chip on red, one on 2-35 column and one on 3-36 column. This way, you will cover most of the numbers on the roulette and cover your loses.
Double your stakes when you lose a bet and bring it back to the least bet after a win. This way you can cancel out any big lose. If you keep doubling after a win, you are bound to lose all the money. You need to keep a strict watch on your bankroll as well.
Other strategies are more complex and are not for beginners. They are Martingale betting system, Labouchere strategy, pivot and shower strategy.
For online gambling, you should think in terms of a long term strategy. Never pay money for the strategies that promise a lot, but deliver nothing. Hence you should play more with the above proven strategies than waste time and money of fraud betting strategies. These fraudulent websites are there just to swindle your hard earned cash.