Today, eBay has over 2 million auctions organized in over 1600 categories. And eBay only lets you list any given item in one category at a time. How can you determine the best place to post your items -- without endless experimentation? And how will potential buyers ever find your items if you don't find that perfect category? How do they navigate through this maze?

While some people, as matter of personality, will naturally browse through categories and subcategories and sub-subcategories, and so on; many simply click on "Search" and enter words that they'd expect to find in the titles of items they are interested in. (The more sophisticated will change the default setting of the search box, clicking to search for words in both titles and descriptions. But, apparently, most people don't know they have that choice).

To get started as a seller, you should think what words you would use in the title for your item and search for those words, then click on a variety of items in the list of matches to see

• what categories they are listed in
• how they are described
• what kinds of starting prices are typical
• how much bidding activity they are getting, and whether the category or other evident factors appear to affect the level of bidding.

If you see that some individuals have multiple items listed in the same category, search by the user name of those particular sellers to see the range of what they have on sale, and whether they are listing the same kind of thing in just one or several different categories.

Also keep an eye out to see if some individuals are bidding for many different items of the same kind. If so, then search by bidder name and see what you can determine about what draws these heavy buyers to one item rather than another.

For new and near-new consumer goods, the category is likely to be very important -- just as it is in navigating through a department store. But for collectibles the category often doesn't matter because so many buyers use search to find what they want.

In other words, try to pick a category that will help your sale, but don't over-estimate the importance of category. In some cases, buyers, using Search, will find you regardless of where at eBay you hide your auction. And, also, if your item doesn't sell the first time around, you can always relist it in a different category.

Think of eBay as made of numerous sub-communities: collectors and buyers of particular kinds of things. Over time, these people build relationships with one another at eBay and through email messages to one another and other online contact. Their expectations of one another depend on their common experience. The behavior of newcomers (people with little or no feedback) is likely to be unpredictable, while that of the veterans will be more consistent. The newcomer might misinterpret a standard description of the quality and condition of an item, and be disappointed with a purchase even though the seller was quite precise and accurate. On the other hand, a newcomer might well bid far higher on an item than an old timer -- not knowing what such items have sold for in the past and how frequently such items are likely to appear again for sale.

You might be reluctant to sell at eBay, even though there is an enormous audience of potential buyers there, because you are afraid that your item will get lost among the millions of others posted there. You might think that you would do better at a focused auction site, devoted just to the kind of thing that you have to sell -- such as baseball cards or comic books. In my experience, that is not the case.

For instance, selling comic books at eBay, I got many bids from people who had no specific interest in comic books at all. They were searching for "dogs" or "Disney" or something else that they avid collect, and my comics happened to have the right words in the title. If I were selling at a comics-only auction site, I'd never get bids from those kinds of buyers. And those buyers, because they are unfamiliar with prices in this particular category, arriving here tangentially, are likely to bid out of all proportion to what you'd get from regular collectors with experience in this sub-community of eBay and with ready access to reference books about prices for this kind of collectible. Remember, you don't need for millions of people to see your item. All it takes is two enthusiastic bidders to raise the price beyond rational levels.

This buyer behavior means that the words in your title are probably more important than the category you choose. Remember, that's the "title." Today eBay's search engine does not look at words in the description -- only the title.