This video shows how you can set up different shipping methods in Drupal Commerce, what they are for and how they work.
I'm using regular expressions in the methods to have different shipping rates for people living on the east coast, the midwest, or the west coast. It's pretty easy to do in Drupal Commerce, once you figure out how it's working.
One thing I'm finding is that a customer needs to have a shipping method set up, or they cannot check-out. That is probably also due to my particular checkout flow, where shipping information is part of the checkout.