In my time on eBay, I have identified five different basic bidding stratagies that people use to win items. eBay uer terrythetroll defines three bidding strategies. His webpage can be found Here

Our main difference is that I split one of his stratgies into three different ones. These three are basically the same, but I feel that there is a semantic difference between each of them that deserves to be identified as a different strategy.

Terry has done a good job of discussing the advantages and disadvantages of these (the three that I split have much the same), so I'll just define them here. First, I begin with the two broad philosophies from which the five strategies are derived.

The Lowballing Philosophy

Lowballing is the act of bidding a very low amount on each auction, often just enough to barely take the lead. This is the way that many live, or Going Going Gone, auctions work, and people often bring this theory with them onto eBay. The fundamental principle of lowballing is don't bid until somebody else does.

The Proxy Bidding Philosophy

Proxy Bidding is the act of entering one bid in the course of the auction. The amount is called your True Max Bid. This amount is so high that you know for certain that you would never, ever bid more for this item no matter what. eBay takes over for you after you bid and uses only enough of your proxy to lead and eventually win the auction. The fundamental principle of Proxy Bidding is bid once, bid your max and don't let your bid affect or be affected by anybody else.

This leads us to the five strategies. Here they are, in what I believe to be ascending order of effectiveness. That is, the least effective strategy is at the top, while the most effective is at the bottom. Lowballing manifests itself in the first three stratagies on top. Proxy Bidding manifests itself in the final two strategies on the bottom.