It's called "sniping"...You wait till the last minute to start bidding, and try to out-bid the other person at the last second...Or you can set your automatic bid at whatever the top price is that you would pay for a item, and then the system will bid for you every time someone else places a bid...
Like if something is priced at 50 bucks, and you set your automatic bid at $200, then once someone places a bid of $55, your automatic bidder will place a bid for you for the next lowest bid allowed...then if that person comes back and out bids you again, system will again turn around and bid for you with the next lowest bid...It will keep this up till either the auction ends, or the system reaches your highest bid of $200 (or whatever you set the MAX at)