For those unfamiliar with "bankroll management" it is a term that can save you a lot of money and trouble in the future. Bankroll management should keep a bettor from going broke if employed properly. The best way to think of your bankroll is by "units". Typically a unit should be 5% of a given bankroll. Therefore a bettor with an account balance of $500 would use units of $25 when betting. If the balance drops to $400 the unit should now be $20. their unit should now be $20. Bankroll management is all about discipline, you must have the will not to bet larger amounts when you are on a bad streak, this will only lead to disaster. Also, you must resist the urge to bet much larger amounts when on a winning streak, as the law of averages is against you.
Players new to sports betting might be better off using an even smaller % as the unit. Also, players who make more volatile bets, such as large parlays and future bets should use a smaller unit for these wagers. The reason being is these bets are much harder to win, thereby increasing your risk. The best way to lower one's risk is to lower the wager.
On straight-bets a 5% unit is best. However, using a 2% unit is much better for parlays, teasers, and futures. Using this method it is extremely difficult to bust your account. The goal is to continue to make bets with correct reasoning while slowly growing your bankroll and money wagered per unit. As long as your bankroll is growing, your bets will be bigger for each event. In the unfortunate event your bankroll should be decreasing, your unit will decrease, but it will always stay at 5%.
In some games a bettor might feel he/she has a large edge on the bet. In these cases it is "ok" to place multiple units on a game/wager. A bettor should never wager more than 20% (or 4 units) on a single game as this brings too much variance should a bet fail. Sports Betting is not for the faint of heart; however, with correct bankroll management accepting the swings of betting can become much easier.