I really do not understand what are you asking here.

Maximum 65% searches through Google search engine that is the main reason whose suggest the web master use Google for marketing. Google provide every country specific Search result only their country like our country name is Pakistan when we search our local search engine Google.com.pk. People getting better benefits target local area and getting traffic through Google.

Most people consider Only Google while doing SEO because it is the most loved search engines on web. Its better if you include Yahoo and other search engines like bing without affecting Google. Almost all search engines just love the unique, quality and relevant content for ranking a webpage in SERPs. So make your page as much valuable as you can for visitors. Try to get backlinks for better ranking. Some thing which you have to consider is length of page titles, Google reads only upto 70 charecters of pagetitle on the other hand yahoo reads more than 100 char in title. You should make your page title in the way that most important keywords for page includes only in 70 char and you can put other keywords in the same tile which can be benefitial for yahoo and bing. But always keep in mind that don't do keyword stuffing.

I think the reason behind it Google is the best name in the market of search engines, its results are more trusted and valuable.

Google is the most popular nowadays so you can rely only on it and get benefits

Originally Posted by jesicawillss

Most webmasters are doing SEO considering Google only. I would like to know which things to keep in mind while doing SEO for Google as well as Yahoo? Means SEO for Yahoo without any effect on Google result.

For google and yahoo some or all on-page factors remains the same, like title meta tag, description and other html tags. Similarly some of the off-page factors remains the same like getting backlinks for website but mainly techniques of getting that backlinks change for yahoo and google. For yahoo search engine ranking you need to register your website with yahoo directory and answers the yahoo question to get backlinks.