What I already do is use a variety of techniques.
At the moment I have some books listed. I know that people often misspell names. So in the auction for some of these I have included variants on the spelling of the author's name - but the text is in either the same, or a very close, colour to the background. This means that the search engines pick up on the fact that the words are there, but the look of the auction isn't ruined by adding lots of junk words.
I have also linked each auction for books in the same series to the other auctions for other books in the same series. This cross-promotion increases the chances of both human and search engine views.
The methods for gaining extra hits on search engines are exactly the same for auctions as they are for regular websites with the exception being that options are limited. We can't, for example, use META NAMES or META WORDS in the header info, but we can carefully use keyword placement within the text of the auction.
Keyword placement is where we carefully consider the specific words that someone might use when searching for the particular object, then we ensure we include them in the description and, if possible, the title, to a lesser extent.
When Nykmedia started this thread I was expecting something new and amazing, not what I was already doing. However, these techniques can and do work. They just require people to make the effort to use them properly.