I have the same problem. Yahoo! actually owns Overture, though, and from what I can tell, their search results rely heavily on Overture's PPC network. In other words, you're going to have to fork over some money for good rankings in Yahoo! At least from my experience. Good luck.
Here is a little cheat I use, code yourself a RSS feed for your website, add it to your yahoo account in the news section and it will automaticly be added to there feed directory and hay presto up your listing with their search engine at the same time :-)
The feed does not have to be complex like a feed from a blog just make the feed links to differant sections of your site :-)
That is rather sneaky, isn't it. I know what you're talking about though. Those feeds where webmasters can add the buttons to their site that say "Add To My Yahoo!" and it will put the site's feed on their My Yahoo! portal.
That will be the one, I'm in the middle or redesigning a website for a snooker hall in the UK but they are on a very tight budget so I have had to come up with some sneaky ways to get them to the top of search engines in the UK for nothing, and this was one of them.
Check it out, do a yahoo search for Snooker in Swindon and bang we are at the top and look at the extra features added to the results RSS: View as XML - Add to My Yahoo!
How did I do it I hear you say clever META tags, loads of people linking to us all connected with snooker, the RSS feed, being the best snooker website in the UK helped and me being a Genious :cheesy:
Since working with Google and Microsoft to support a single format for submission with Sitemaps, we have continued to discuss further enhancements to make it easy for webmasters to get their content to all search engines quickly.
If you can afford it you may want to submit your site to the yahoo directory, i submitted mine last year and have since seen a sharp increase in my Yahoo SERPs. Other standard tips are good content and keywords in your title tag.
Submission of your site to yahoo directory will not give accurate result from your site. It is better if you do it in a natural way like the doing the on-page optimization. Overall key density in the text content should be between 10 and 20%, with primary keyword density about 5-6% and secondary key word density about 2-3%.