Ok, guys, he's not asking HOW to pick a winner(s). He's asking what to do after he's done that. Stop telling him to bet an overlay.
I've been around here a short amount of time, but it seems like most guys around here play multi-race wagers and reduce their level of risk by covering. There's a good thread on multi-race wagering that BTW weighed in on called SA Pick 6 carryover, or something to that effect. There are some good lessons in that.
As far as money management goes, from a basic level what I would suggest is figuring out exactly what your bankroll is and exactly how much you can afford to wager when you do play. So, if you have $10,000 per year bankroll and you play 100 times a year, you can plan on having, on average $100 every day you play. This is helpful because it tells you what types of wagers you can play consistently and, realistically, have a chance of success. If one has $100 to play when he/she wagers, they are not pick 6 players most likely...more like rolling Pk 3 and Pk 4. Maybe not even that depending on the aversion to risk a player has personally.
Also, what I think you might be hinting at with money management is the notion of changing the amount bet depending on your position as you go along. For instance, some folks say if you're losing you should bet more to make up for what you lost when you eventually do win. This is suspect, but some folks subscribe to the theory that, at some point, they're "due." I say baloney, every race is a new set of circumstances, you could go on forever and keep picking a number based on handicapping and still have relatively little success. In other words, I don't think it's as analogous to flipping a coin and, over time, having heads and tails come up an equal number of times.
My latest money management strategy?? Quit when I'm ahead!! And play within my bankroll. Or at least, when I'm ahead, don't bet it all back. If anything, I've learned that betting back most or all of the amount that I'm ahead using aggressive bets usually ends up being unprofitable. For what it's worth...
