As far as buying/saving on
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. May be telling them that they would not have to wait as long to get their money (they would probably know that, but it still might help). If that does not work, use a sniping service such as Bidball.com to bid for you. It'll bid in the last few seconds, helping you to save money 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 list of results that you receive in the e-mails. Excellent for "Buy It Now"s priced right.
If the item that you are looking for is difficult to spell, try a misspelling search site like Typojoe.com to hopefully find some deals with items that have main keywords misspelled in the title. Other interested buyers may never see them.