Good question. I never go back and do this and that is probably why my revenue from Amazon is so dismal.
Frankly I have never seen or found, not that I have spent a lot of time looking, for a tutorial on the best way to determine what the best product would be.
I would think that if Amazon had their stuff together their software would match your Hub Page content to their relevant product and do such a good job matching that both Amazon and we Hubbers would benefit.
But I guess not every company can have it together as much as the big G - Google.
So if anyone else answering this question can direct me to a tutorial on picking the best Amazon products without taking an inordinate amount of time, I would greatly appreciate it.