The most important thing people look at when they do business with you on eBay is your reputation as a buyer, or your "feedback rating." They will decide whether or not they can trust you based on this small number.
People can leave feedback for you when you buy or sell something on eBay, and you can do the same for them. This feedback can be good, bad, or neutral, and it can also have a comment. Then, your feedback rating is figured out with a simple subtraction: the number of positive comments minus the number of negative ones. This means that a person with a feedback rating of 28 might have 30 positive ratings and 2 negative ones.
If you are a good buyer, positive feedback should show up next to your username without you having to do anything. There are, however, a few things you can do to help it along.
Always leave feedback for others. If you leave feedback for them, they'll feel like they have to do the same for you (eBay will send you an email after each transaction to offer you the opportunity). If you take the time to write nice things about sellers who do what they should, it's likely that they'll do the same for you.
Pay quickly. Sellers love getting paid quickly. If you pay as soon as the auction ends, especially with a credit card or another electronic method, you save the seller a lot of stress. If you pay as soon as the auction ends, your positive feedback will usually show up just a few minutes after you pay.
Don't be a hard-to-please client: Know that it might take your seller a day or two to respond to you and maybe a few days to send your item. Getting in their way is rude and pointless, and it won't help you get good feedback.
Build relationships by buying from the same seller more than once if they sell a lot of things you like. They will be very happy to find a regular customer and will go out of their way to leave positive feedback like "a joy to deal with as always." Also, they might have some deals for you!
Most sellers won't hesitate to sell to buyers who don't have a good reputation, because the buyer takes most of the risk in a transaction. It's important to remember, though, that both transactions in which you are the seller and those in which you are the buyer count toward your total feedback. If you ever want to start selling, it's especially important to be a good buyer.
People care a lot more about sellers' ratings than buyers' ratings on eBay. Most sellers don't bother to check their buyers' feedback, but bad feedback on a seller can (and should) kill a deal. So, when you're buying, you should care more about the reputation of the seller than your own. That's why the next email will be all about the feedback ratings of sellers.