I have bought a lot of stuff from online auctions. My winning percentage is about 10%, given that I am cheap and patient. The good thing about Ebay for example, is that if you don't see it this month, something better will be coming next month, or 5 years from now.

Bidding strategy: always snipe. Bid in the last 10 seconds. This strategy kills the shill bidders, the newbies who have no feedback and nothing to lose if they do not pay, and the type-A psychos who are out to 'win' regardless of the final damage.

Shill bidders: lots of this going on - especially on large dollar items. Sometimes I will bid early and then passed by some low feedback numbskull. If I suspect it is a shill, I will review this guys previous bidding patterns and come in just under his bid. Nothing more satisfying then watch a shill win 10 of his own auctions, and have to eat auction fees.

Feedback: once a buyer has paid according to the auction rules, then the seller should send positive feedback. Sellers who wait on feedback are just trying to hold the prospect of revenge feedback over the head of the buyer. When a buyer pays, then his responsibility to the seller is fully discharged. What to do with these sellers: do not send them feedback. Never bid on anything they sell - ever again. If they've pissed you off some other way, then send them a negative 10 seconds before the close time on feedback.