Up to now, I have only bought a few items at auction, I've used AuctionStealer with success, Now I usually hit the buy now button when buying off ebay.
I do my home work on the product, find out how much it's worth, make sure it is a Aussie store with good feedback.
Sometimes my local Spare parts bloke is cheaper than eBay.
As Lost mentioned, I bid, and forget it, IF i am the winning bid so be it, if not I haven't forced up the price by getting carried away.