Digging into the E-conomy

How exactly do people make money from blogs? It seems as though there are a number of different routes: adverts - from the likes of Google, adverts - which they have sold themselves, sponsorship, commission on selling other products via e.g., Amazon, and perhaps many others. Anyway, I was pondering this, the other day, when I mentioned the Bill Bryson book, so I thought I would dig deeper to learn how the systems work. It is AMAZING! There seems to be a vast industry covering everything from Search Engine Optimisation (how to get your site appearing in the best place within Google), through to people who write your copy, others who offer to put lots of links to your site on their sites etc. I decided to start in some very simple ways, so I have signed up for Google's AdSense system - at the moment the adverts are all about 'carts' and I have no idea why! I also signed up for Amazon. However, this introduced my first problem. I signed up with Amazon US, which is fine if the audience were American, i.e., when they click on a book recommendation it naturally takes them to the cheapest place for them to buy the book. But, if you are in the UK it makes more sense for you to go to Amazon.co.uk. So what happens to my fortune in commission? Do I have to sign up with multiple Amazon countries, or is there system smart enough to track the visitors? Lot's of questions, relatively few answers - time to start digging!