Too many to count.
Try making your last bid as high as you are willing to go, first off. Don't make it the minimum amount over the previous bid. That's just asking to lose. And make it for an odd amount - in other words look at what the bid would be if the person bid the minimum after you. If it would be, say, $15.50, make your bid something like $15.87.
Should help.
But don't be a sucker and bid just to win. There are always other auctions and if some dumbshit is willing to pay too much -- well, just be glad you're not the dumbshit.