Affiliate Marketing Secrets

Affiliate marketing is brand new to me and I’ve got a few possibly silly questions after buying/reviewing Deadbeat Super Affiliate.
Are you supposed to register as an affiliate with Amazon? or with Clickbank? or?
Amazon says they review and approve/reject your advertising site…so should you post the first article beFORE signing up with amazon?
Say I sign up for awesomereviews.com as my main domain. Would I then sign up for other domains for each niche like uggbootsarecool.com (linking back to the main one) and then different articles on those sites linking back? or Would I just create new databases on the main awesomereviews.com site for each niche?
I’ve never done anything like this and I think I have confused myself on exactly where to begin. I followed the steps in the Core Training, and I’ve purchased a domain (which has nothing to do with any niches…it’s a music site for personal use) and I was about to sign up for a new domain with the first niche I wanted to try and link it back. Just not sure on which one to post my articles and where/when to sign up to start making sales.
Would I give the Amazon affiliate application form the url to my personal/music domain? or to my niche domain?
Why is a domain name $500-$1400 on enom.com but only $11.99 on Godaddy.com?
Does anyone recommend getting just a .com, or is it best to get .com, .net and .org if possible for each niche? OR do you get all three for the main site and then just link all niches back?
Any sort of guidance would be graciously appreciated! 🙂