Mulitple Terms in Multiple engines

Hello All! I have a question for all you gurus out there. I have various sites which I am trying to optimize. When looking through the 4 major engines (Google, Yahoo, Ask, MSN) I am noticing that any one site will do well in different engines for different keywords. My question is this...is it better to optimize a site for mulitple keywords in one engine, or is better to take advantage of current organic rankings by optimizing one site for different keywords on multiple engines. For example, if I have a site geared toward SEO and I notice that I rank #4 in Google for 'seo' and #5 for 'link building' in Yahoo but I am #75 for the term 'link building' in google and #30 for 'seo' in Yahoo, is it more beneficial for me to optimize my site for 'seo' and 'link building' in Yahoo or Google, or is it more beneficial for me to optimize my site for the term 'seo' in Google and the term 'link building' in Yahoo and hopefully gain a #1,2,3 position for both terms in separate engines? I hope this is not too confusing...any opinons, advice, expertise would be greatly appreciated.

Each search engine have it's own algorithm for ranking sites so first of all target your keywords and try your hands for different SE, once you start getting results then compare each with other and whichever is closer to high rank work on it.
It is not necessary that a keyword ranking high will also rank high at other SE; this may due to competition for that keyword at that SE.

What i will suggest you to start with lesser popular keyword so that when it ranks well you get some confidence...

IMO, just go for Google. It is the undisputed king, and won't be losing its throne any time soon.

When you consider that Google has over 60% of the market share and Yahoo & MSN combined don't even match 50% of Google's market then it would be best to optimize for Google.

However, why would you want to turn down the other Search Engine's traffic to your site: it makes no business sense. Overall I optimise for all three, its in the contract that I sign with my clients and to be honest if you do your job correctly then you will achieve top results right across the board.

If you don't do the following, you might be a redneck:
Setup you html semantically,
don't use frames of any kind,
have an appropriate title,
use meta tags for SEs that actually use them,
have a nice layout,
put keywords in heading tags,
ect.....

I could go on for a few more minutes, but I don't wanna.....

I agree, it is good to use meta tags for all search engines. Also work out to get good natural backlinks.