Question on evaluating an amazon affiliate site

Hi All,

If I am to evaluate the revenues of an amazon affiliate site, what would be items that I should check. I have the following list. Are these ok, or should these be refined? Should there be any additional gotchas?

1. Get added to analytics and validate traffic
2. Research backlinks and validate
3. Validate earnings on Amazon Affiliate site. Could 2 sites handle the same affiliate tracking id?

Any other things. One questions is, as explained in number 3 above, can someone use the same amazon tracking id on more than one website? That would mean that one website may give more earnings that the other. If it is possible to have more than one website for one unique tracking id, how can we differentiate the sources or attribution to each site?

Thank you for your time.