A friend recently asked for an ebay primer and I was more than happy to share what I've learned from trial and error and more error in the vast e-mercantile that is eBay. Every few months, I get on a cleaning bender and find several items that could be eBay worthy. This leads me to my first tip: 1. Set aside a box for selling things in-season. Buyers generally don't want to load up on a snowsuit in July. Likewise, few people will be scanning the sales for a tube top in January. Some may, but the bidding wars seem to happen when you have a large stock of in-season goods.
2. Items that sell well, based on my experience: Brand new cosmetics Designer shoes, handbags Children's clothes from Hanna Anderson, mini-Boden, crewkuts, Matilda Jane, other chi chi purveyors Maternity clothes - especially office attire Work-out videos
3. For used baby items: group them in a lot. Sell in a 3 day sale, list Thursday with sales ending Sunday evening. I usually only charge $1 or so for shipping and have found that the bids on these lots rise more quickly.
4. For unused items with the tags still attached, list at a price that you feel a consignment store would charge.
5. Always, always get tracking on packages and hang on to the tracking info. until you are sure the package has been received.
6. Answer questions from potential buyers with as much information as is requested. Be transparent about any flaws in the item.
7. Try to resolve any disputes through messages with buyers; a passive-aggressive low rating of a seller will only hurt you as a seller (lest the buyer retaliate).
8. Reuse boxes, envelopes, packaging. Good for the earth and envelopes can be expensive and will cut into your profit.
Feel really free to share in the comments field any tried and true advise that has worked for you.