Submit your sitemap to Bing, heading tags and make seo on page well. Also a important factor to SEO on Yahoo is domain age, if you have a domain existed in more year, I sure that it will be easy to get high rankings on Yahoo than others.
If you want to increase your yahoo ranking please do seo as well. Submit your site yahoo webmaster tool and submit your sitemap. "SamuraiSEO" this site is very helpful for any seo problem. You can take more help there.
If you want to increase your page rank and website traffic you to do off page optimization technique
Here i mentioned some of the best off page optimization technique :
1) Article creation and submission.
2) Blog creation and submission.
3) E-book creation and submission.
4) Directory submission
The best way to increase the website's ranking at Yahoo is we need to optimize our website to Bing Search. Why i am talking about bing? Because, Yahoo's search algorithms has been merged into Bing search.