I UL'd some clips to CD last month, and I just checked out some of the search results.

In EVERY search I checked, my clips are dead last by relevance. Every one of them.

Is there some secret to moving up in the relevance search, or does it normally sort the newest files at the end?

No sales is discouraging enough, but sort of expected based on what I'd read. But to have all my files lumped together at the bottom of every search is piling on the discouragement!

Hopefully the ones you've had sales on have moved up considerably in the relevance search results.

I guess the algorithm they use must be weighted towards sales by keyword. I wish they would give at least a few new ones a bit of a push. Oh, well, maybe I'll get a sale and I'll feel like UL'ing more. 

Sounds like you know this already, but it may take some time (or not depending on the quality of your offerings) for your clips to move up into the first search results. Each sites engine is homemade, so they work differently but, they are triggered by a few events with determine relevancy. The first one mostly likely being - have you sold clips on the site before. The search is probably weighted in a combination favoring proven sellers both as a clip and as a seller. The second being the ratio of views to sales, which is the same thing, but in reverse - many hits and no sales decrease your relevancy. It's hard to peer into the search engines, as they are not giving up their secrets. A combination of strong key-wording, sellable footage should tell you something over time.