I use a Money Management system that is divided on three different levels: Single Dime Play (3 units), Double Dime Play (4 units) and Triple Dime Play (5 units). I feel pretty comfortable with this system and I believe this is one of the reasons why I've been so successful in this business.
My recommendation is to establish a bankroll of 300 units (you select how much $$$ an unit is worth) and then, you should bet the following on each play:
SINGLE DIME PLAY = 1.00% of the bankroll
DOUBLE DIME PLAY = 1.33% of the bankroll
TRIPLE DIME PLAY = 1.67% of the bankroll
E.g. Someone with a bank where 1 unit = $100 (bankroll: 300 units x $100 = $30000), should bet $300 (3 units) on a Single Dime Play, $400 (4 units) on a Double Dime Play and $500 (5 units) on a Triple Dime Play.