Simply put don't make your pages for SEO, make them for your users/visitors, do your main SEO offsite.
Time and time again though, we've experienced the google high - bing/yahoo low or the google low - yahoo/bing high.
It would seem each search engine reviews the others and do not want to display the same results, after all, what would be the point?
So figure out which one you want to target and go for it with whatever methods that get you up there. I think it'd be quite hard to get #1 for all search engines, unless of course your a site like wiki.
Good luck!