There are probably two key points in my opinion to be successful and I tried showing that in this thread:
1) Have value on your side in every bet.
2) Play at total odds which you can succeed at in the long-run.
Adressing those points:
Value
The only way in the long-term to beat the bookmaker is to take 'value' bets. Most punters never understand this term or follow it. It is quite simple really because when you are betting you are not betting on an outcome but really a price. Therefore the price you take for a certain event should be greater than the probability of it occuring. True value also takes this into having a good chance of winning too.
So for example betting on Juventus @ 1.50 in a home match indicates they have a 1/1.50*100 => 67% chance of winning. If you think they only have a 50% chance of winning then this bet shouldn't be taken because if this match was played 100 times maybe they would only win 50 and 50 times draw or lose. But of course many take the risk believing as long as they win that time you have your money on them it is ok - which is wrong because in the long-run you will lose. However, if Juventus has more than a 67% chance of winning then this bet should be taken.
Another simple example is rolling a dice:
I roll a dice and if it lands as a 1,2,3,4 or 5 you win and I only win it is a 6. Of course you would take this offer as you have a 5 in 6 (83%) chance of winning compared to my 16% chance. That is simple probability.
But when prices are introduced:
When you win I give you £0.20 however when you lose you give me £1.00. Now would you take this bet as even if you win the first 5 times but then lose the 6th you've only just broke even. It's more liekely you would lose before the sixth time however. Your chance of winning was the same as before but now once the risk is introduced with the prices it can be seen you have no edge.
Another example is a coin toss which has a 50-50 outcome. You wouldn't bet on this if the price was 1.91 but would if it was over 2.00 for the same reason of increased percentage expectance.
Success rate
It's exciting going for combination bets which return 10 times your stake but I've already shown the low chance of success. But secondly to be successful such as that you need to win at the rate the odds suggest just to break even. For instance with bets around 2.00 you need to win at 1/2.00 => 50% to break even. Winning >50% enables a profit. This is linked also to the value aspect of betting but in the long-run it's worth having a price range you enjoy and find success in. Many find this range somewhere between 1.50-2.50 but you should choose wherever you can make wins to survive.
Buy on AliExpress.com
which reminds me why I rarely bet on sub-standard players. 
