eBay has spawned an entire industry of companies whose business is making it easier for you to sell. Some, like Andale and Terapeak, have official links to eBay as "certified providers"; others don't. (eBay screens certified providers before they can fly the eBay logo on their site; certified providers have to pass a certification exam, provide references, and prove extensive experience on eBay. You can see a list of certified providers and the products and services they offer at http://developer.ebay.com/programs/certifiedprovider/catalog.) There are about as many software programs as there are tasks to organize and automate. A few are free, and most of those that aren't offer a free trial. Shop around and try several, until you find the program that best fits your business needs and work style.
If you want to see what others have to say about these programs before you commit, check out the software-review resources on Section A.5.
The main disadvantage of using tools and services provided by companies not affiliated with eBay is that when eBay makes a change, the tool can break. It can take a week, sometimes longer, for the company to catch up and get the tool working again.
Researching the market—in other words, the stuff everybody else is selling on eBay and who's buying it—helps you decide what products to sell and what to chargefor them (Section 7.1.1). Do prices drop on 3- or 4-megapixel cameras when a snazzy 7-megapixel model comes out? ...