How to backup and transfer apps from one Android Smartphone to another?

We don't use a smartphone forever, right? We all want to upgrade to that shiny new gadget in the market, which has features we may need or not. May be just to use the latest gadget. For whatever reasons, we do get a new smartphone from time to time. Getting a new smartphone can be exciting. Setting up is easy too. But transferring all of our apps, contacts, photos, and more to a new device