For the most things that commonly matter - it is automatic. Your GMail, Google Music (or Amazon for that matter), Photos (If you have G+ app installed), Contact

For the most things that commonly matter - it is automatic. Your GMail, Google Music (or Amazon for that matter), Photos (If you have G+ app installed), Contacts, App list, wallpaper, WiFi and other settings are all automatically backed up to the cloud and restored when you factory reset or get a new phone and sign in to your Google account. For things such as SMS and full system backup - you have to take things in your own hand. SMS is easy with a 3rd party app, full system backup can be done using Titanium if your phone is rooted or by using command line scripts using adb. (adb supports encrypted backup to the desktop.) Also various OEMs provide their own Desktop sync program - like Samsung Kies - that make it easy to backup/restore using a PC. But it is fairly unnecessary to go to that length - default backup + SMS backup app works quite well for most.