Pay Per Click uses an algorithm, and crawler bot to determine page relevancy to ads and keywords being bid on. About the same thing they do to organic SERPs. A little SEO tip......do the meta keywords well on each of your pages making sure keywords in the tag are used in your page content and Yahoo will boost your rankings.
Huh, never tried that. I know with Google organic meta kw's do nothing, but never really had to do much with the ppc stuff, since I always have made nice ROI.
I have not seen anything new here, that I didn't cover in my Google Ranking Factors page, which has been up for years - http://www.vaughns-1-pagers.com/internet/google-ranking-factors.htm If I find anything new, I will add it (once I confirm its veracity). Of course, on many items, there is no universal agreement. I even disagree with Danny Sullivan on several items (meta). Early on, I learned most things from him. Rand Fishkin is probably the top Google SEO today, over at http://seomoz.org. But you must join to see his best stuff. Rand demonstrates an open-mindedness that is rare and refreshing. Most others are cock-sure of themselves, and are frequently incorrect ("My mind is made up - don't confuse me with the facts".)