Their algo is similar to Google's the standard things you do for SEO will get you top placement on all 3 big search engines Google, Yahoo, and Bing.

first time to hear that the have similar algo with google. i thought they have their own algo when it comes to rankings.

Right, different search engine would use different algorithm. But I think the basic rules on SEO are applied to all search engines.
I would like to recommend you to read this article "search engine ranking factors" from seomoz.

Wish this help,

The fastest way to show up in Yahoo's search results is to pay Yahoo to join their Search Submit Program. Once you've submitted your site, Yahoo will send out a SLURP crawler to index the site and put it up for review by one of Yahoo's editors.

as for my sites, there are very small traffic comes from yahoo except yahoo answers, so i think i'd do my best in google results.

Yahoo answering is one of best way of getting ranking in yahoo, beside this choose your domain name keyword oriented and submit your site to yahoo directory.

If you do your seo good for google, you don't have to worry about your yahoo rankings.