Basically you have to find a system that has a statistically significant mathematical advantage for the bettor. Trust me, these edges are not easily found. But if you are willing to search hard enough and crunch numbers enough, they can be found.
If you are thinking about systems that use manipulation of bets somehow (martingale, larouche, etc), forget it - they don't work. People will swear up and down that they have used a system to success or modified it somehow to make it effective - it's all hogwash. In the end, you will lose. Read and repeat.
The only way to win long term is to find out probabilities of certain events and find particular ways to exploit that through mathematical bets. I have one system for hockey and two for MLB...between all 3, I can make about 125-200u per year. But it is the ultimate grind - the edge isn't super large, but it is significant enough that if you stick to your gameplan, you will most definitely make money in the long run. The
odds are in my favor. No I cannot share any of them, as they would exploited by sharps to no end and the value would be lost for me. But I am working hard to find others...thought I had one the other day, but the math didn't back it up so I can't use it.
Let's say I know I the probability of an event happening is 20% - and that event % has been generated from a sample size of over 10K events. When that event happens, I will lose 1 unit, but the other 80% of the time, I win 0.3 units...so over the long run, I should win 0.2 units over every 5 bets ( (4 * 0.3) - 1 = 0.2)...those are the type of scenarios I am interested in. Trust me I've crunched a ton of them and have only found 3 so far that work...