I cannot overemphasize this enough...Research, Research and Research

It costs nothing to browse eBay, and that's part of the charm. But you can make that work for you as a seller: search for your item, not only to work out what to charge for it, but also to gauge interest. If an item is consistently listed with no bids, perhaps there's little demand, or sellers are asking too much. Can you undercut them and still make a profitable sale? It's also a good idea to see how different items are promoted; while it's a copyright infringement to steal someone else's listing description, there's nothing to stop you using the same basic ideas in yours.

Do your research before listing. Knowledgable bidders love it when sellers are too lazy to research their items before putting them up for sale on eBay. Those sellers consistently offer them bargain after bargain, which can be sold again on eBay with a better title and description for lots more money. Use your books on antiques and collectibles, Web sites like this one and conversations with other sellers to learn about what you're selling on eBay long before you attempt to auction it off.