How can I find LEGO bargains on eBay?
I don't think there is a single strategy that will always work - it all depends on what other people are looking for at the same time as you are looking. For example, I have seen Lego Maersk train sets (I'm a Train fan :) ) sell for $250 in certain auctions, but have managed to pick up one with extra power functions for less than that in a separate auction.

Here are a few things that might make your life easier:


Create searches and save them (you can even get notification emails for new finds this way). These are called "Followed Searches".
Use the tips and techniques in the Advanced Search section of eBay Help to refine your searches. For example, if you want LEGO but not Duplo, you could search for "Lego -Duplo".
Always compare with current retail values (check Amazon.com, shop.lego.com or brickset.com) if the set is still current
For sets that are no longer current - look at brickset.com to see what they used to go for. If you have the time, check out Bricklink.com and see how much the same set costs there, or, if you really have the time, use the Inventory feature and see if you can get a better deal just buying the set pieces :). For the popular holiday train (10173) for example, which easily sells for >$500 on eBay, the cost in pieces is typically around $200 on Bricklink, lower if you already have some of the critical pieces.
When it gets to bidding, look into using Sniping software, which allows you to place a bid in the closing seconds of an auction. This often helps you win auctions if no others are using snipes. JBidWatcher is a good starting point.
For bidding, check out what others have already bid ("Bid History") and also look at "Show Automatic Bids". This allows you to see who is really eager to get it and how often they have bid.


There are for sure other techniques out there, but these are the ones I find work best for me.