If anybody's interested this is a guaranteed way to be successful selling on Ebay. The advice is simple and should be obvious but ...
1) Try buying items before you sell. When you get good and frustrated (and you will), ask yourself, "what kind of person whould I like to buy from?"
2) Once you decide the kind of seller you'de like to buy from, become that seller.
I sell Baseball cards. Anybody that ever purchased a Baseball card on Ebay knows about the postage scam. I will never buy from a person who charges $3 to ship a Baseball card (it is ridiculous and insulting). I get ALOT of repeat bidders / business because when you buy a $5 item from me it actually costs $5 (no postage mark-up, no handling fees...).
It is a basic business principle (principal?)... keep your customer happy and they will return. If you are trying to figure out ways to squeeze an extra buck or two from your buyers, you might actually get it. While that is a good short term strategy it is poor long term business. Your customers are not stupid. Don't treat them like they are.
The trick to being successful on Ebay is to be bookmarked by as many people as possible. A buyer will only bookmark you if they like you. Do something that sets you apart from the "usual seller". The more people that look, the more bids you will get. Bids = profit.