Niche Research Method for Affiliate Products

Is there such a thing? Is it necessary? Or do you just pick anything, maybe something you like and build a site, seo it, etc.
I am stuck, mostly I think from too much info and lack of a decisive method, on creating a criteria for profitable niches and am inclined to believe that developing a research methodology is foundational to making a living online as an affiliate. If this isn't a correct assumption I would love to hear other perspectives. I have a number of courses (I would be embarrassed if I told you how many) with varying degrees of advice regarding market research. Some of the courses complement each other, some contradict but I have yet to see a comprehensive methodology that is efficient and effective for selecting your own profitable niches- not ready made ones given to 100s of others. Maybe its not necessary if you have superior internet marketing skills...? There are so many tools; CB marketplace, cb analytics, cb engine, amazon categories, google trends, market samurai, wordze, yahoo buzz, paypal shops, ezines, etc. I am looking for advice regarding a cracker-jack method that works...or is that wishful thinking? Successful and experienced marketers care to share...thanks in advance for those that do.