Do you know how to optimize for google?? If yes then you will get yahoo right eventually .. but with lots and lots of patience. Yahoo seems to be taking extra long to process any optimization changes.
First think of keywords that you want to target which you think that your targeted visitors would likely to type on search engine. Use Keyword suggestion tool, target a keyword which is not too competitive and not less competitive. Then create a content for your site using your targeted keywords. Use also your targeted as your anchor text.
As much of a pain as Google can be, Yahoo can be too. Using good keyword descriptive anchor text for your internal site page links helps a bunch with both Yahoo and Google.
Use relevant Meta tags for every single page of your site, include as much content and update your site with new content as often as possible, and update a sitemap both on your website and with the Yahoo sitemaps function. Yahoo prefers a much greater keyword density level than Google.
i feel that yahoo has taken AGEs into their algorithm too.. I only see my aged domain rank well in yahoo. (about 3 years old)
As per my knowledge, Yahoo consider age as a factor more than google, Meta tags are still very important for yahoo. Rest everything remains the same.
if you serious about yahoo and msn.... then you need to modify your url according to your theme.... Suppose your keyword is "web development"... then try... yourdomain.com/web-development.htm