As far as buying/saving on eBay goes:

If you see an item that you want listed in auction format, send the seller a message asking if they will accept $x to end the auction early and sell the item to you. If that doesn’t work, use a sniping service such as Bidball.com to bid for you. It’ll bid in the last few seconds, helping to save $ and avoid shill bidding.

If there is a particular item that you want that is relatively rare on eBay or goes fast when one is listed, use ebuyersedge.com to set up a saved eBay search for it. You’d get an e-mail whenever a match is listed. You can use the price, category, exclude word, etc. filters to narrow down the results that you get in the e-mails. Excellent for “Buy It Now”s priced right.

If the item that you’re looking for is difficult to spell, try a misspelling search site like Typojoe.com to find some deals with items that have main keywords misspelled in the title. Other interested buyers may never see them.