Thought I'd relay this one on this thread as it relates to systematic approaches (in most cases)

A friend of mine opened an account offering a $500 deposit bonus, which had to be used in one bet (fair enough) and the initial deposit and any winnings from the free bet had to be turned over at least once (again fair enough)

Ok so my mate is lucky that his $500 free bet gets up @$3 so he is $1000 in front + his initial $500 dep. Now he reverts back to his usual $50 bets, but couldn't understand how the withdraw able balance kept reducing every time he had a bet, until he realised that every subsequent bet was being deducted from his withdraw able balance and NOT from his account balance, hope I haven't made that sound too complicated.

Now the crux is, in this scenario, TAKE the withdraw able balance immediately it becomes available, that way your next bet is deducted from the remaining account balance, if it wins immediately take the withdraw able balance again and so on. Hope that helps out some fellow systemites! Of course aferwards you can pay in and carry on betting as normal.