That's what a seller's feedback history is for. It's hardly perfect, but you can get a good idea of what buyer's past experiences have been. Avoid sellers with a private feedback rating (why would you hide the very thing that is supposed to bolster your trust level as a seller?.?.?.) or sellers who mark their auctions "private", so you can't see the auction number in the feedback rating (IMHO there is absolutely no reason for a seller to completely disclose their past sales. If you've got something to hide, that makes me suspicious.) Don't trust feedback completely, as it can be easily faked. Or in the case of authenticity, naive buyers who don't know what they're getting. For example, there is this one eBay seller with a high feedback rating (1000+, one negative for every 150 positives) whose merchandise is so obviously fake, yet he continues to sell because of a seemingly high trust level due to a high feedback rating. Ask sellers questions. Discounted merchandise has to come from somewhere. Most often, it's an outlet if it's advertised "new with tags". Sometimes you can find buyer/runway samples. Other sources include estate sales, liquidations, etc. Be wary if you hear a story similar to the proverbial "guy selling in an alley in the back of a van" - i.e. I know a guy who works with a guy who works with a factory's janitor and they got some extras made with the ends of cloth. In general, I've found reputable sellers will answer questions thoroughly, professionally, and without a run around. Also, take the time to track a seller's activities for a few days/weeks. A seller posting up the same item over and over again (maybe in different sizes) is a bit fishy IMHO. Learn how to recognize tags/labels, which can change from year to year. That's all I can think of for now, I'm sure everyone else will pipe in with ideas/comments.