Although the vast majority of shoppers use eBay's search feature to comb the entire eBay auction marketplace, some buyers will go straight to a category that interests them and “window shop,” thereby running across your item without specifically looking for it. In addition, using the category function provides you and other sellers an effective way to collect sales data for a category, allowing you to assess whether interest in a category is growing or declining and which categories are generating the most traffic.
The new version of eBay’s Sell Your Item form suggests categories based on the other similar items in those categories. If you have used the same category previously, you can click on “choose a previously used category.” You can also enter keywords to search for a category on the Select Category page, which function will guide you through a hierarchy of category listings (see below). Choose Browse Categories on the Select Category page.
eBay's Select Category Page
Should you list in a second category? Probably not. Unless you are convinced that it will really double your exposure (for example, if you had Wireless Noise-Canceling Headphones and wanted to list them in the Wireless Headphones and Noise-Canceling Headphones categories), there's probably not much logic in paying double the listing (or “insertion”) fees.
Mature audiences. There are separate rules if you plan on selling anything in one of the Mature Audiences subcategories.