Does landing page affect your QS in Adwords and YSM or just the performance of your ad? Can redirects or cloaking be used? Which is etter, huge long tail KW lists or short target KW lists? Do you write a different ad per KW or and ad for many KW's? Do you target KW with competition or look for one without competition?
landing page does effect QS, your ad should have the same keywords as your landing page and be relative redirects - with YSM not much of a big deal yet, but with Google your display and destination url have to be same. are you redirecting to the affiliate merchant? keep in mind that if everybody is using the same page (merchants page), you're not going to stand out. KW lists - you have to test, too many variables, different things work differently for everybody your ads should target your keywords it helps your QS and CTR KW w/competition - different opinons, many people like competition, if there is competition then you know there is money in that niche. you can find niches without competition as well. Just do everything you can think of, and keep testing. Nobody has a concrete answer, this is all learning, working, and improving.