As a recovering eBay addict, I now do more browsing than actual buying, I have noticed that a common mistake eBay sellers make is to set the minimum price for their items way too high. The items don't sell because with just a few clicks a buyer can find out the book I'm looking at on eBay is selling for less on amazon.com or if the decorative collectible I'm looking at usually sells for a lot less. When the rare object you are swooning over is fabulous, but the price is inflated, that's when it's time to negotiate.
Ebay allows you to watch the item without bidding on it by going into My Ebay and selecting the Watching function. Keep an eye on the item right up until about 24 hours before the bidding is set to expire. After the overpriced item has been on eBay for days with nobody bidding on it, the seller might start to realize that greed doesn't pay and not only aren't they going to get the price they wanted, they might not sell the item at all. This is the time to email the seller and start negotiating for a lower price.
To learn what that item typically sells for type in a few keywords into the search box and then click on the Completed Listings link on the left hand side of the page. The Completed Listings show me what a certain item has actually sold for in the past. This gives you a better idea of what people are actually willing to pay for an item, not the price sellers are hoping to get.
Contact the seller about 24 hours before bidding ends and let them know you would be interested in buying the item if they would consider selling it for a lower price. In your email you can let the seller know that what they are selling typically sells for $100.00, not $200.00 and you would be willing to buy the item if it was closer to the $100.00 price. Don't get cocky and suggest the seller might as well sell it to you since no one else is buying it. Irritating sellers is no way to negotiate.
By the time you are done emailing the seller back and forth to work out the details, the eBay auction may be over, leaving you dealing directly with the seller. Try to get the seller to agree to payment through Paypal since, Paypal doesn't give your credit card information to the seller. The next best payment option would probably be a credit card since credit card companies do offer some forms of protection if the seller doesn't deliver what they promised.
If the item is a bit pricey even after you've negotiated the price down, ask the seller to email you a tracking number for the shipped package to make sure your fabulous find doesn't get lost in transit. After receiving the goods it's good buyer etiquette to leave a positive review of the seller on eBay. If you ended up purchasing the items outside of eBay you can simply send them an email telling them how much you like the item and thanking them for sending the item in such a timely manner. Showing some appreciation is always good business no matter how big or small your purchase is.