ADB Backup & Restore
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So you have had your Android device for a while and you want start customizing, but you know if you unlock the bootloader and root your phone it will wipe everything. So what do you do?  Use ADB backup before you root, then restore once root is complete! 
You must have Android SDK and your Android phone drivers installed on your computer.

How To Backup

  1. Verify your phone is On, plugged into the back of the computer, and USB debugging is turned on
  2. Copy sdcard contents to your computer, such as music, files and pictures
  3. Open the “C:\android-sdk-windows\platform-tools” folder
  4. Open a command prompt
    1. Press and hold the shift key and right click in the folder window
    2. Select Open Command Window Here
  5. In the command prompt type “adb backup –apk –shared –all –f /backup/mybackup.ab” and press Enter
    1. This will create a backup folder, and save the backup to “c:/backup/mybackup.ab”
    2. It will backup your app data + the apks
  6. On your phone you should see the screen on the right
  7. Create a simple password
    1. Make this easy to remember
    2. You must not forget this password
  8. Select Back up my data
    1. This may take several minutes. When its complete a screen will say backup complete, and the phone with return to the homescreen
  9. On the computer, go to the “C:\backup\” and verify there is a file labeled mybackup.ab
  10. You have successfully backed up your phone

How To Restore

  1. Verify your phone is On, plugged into the back of the computer, and USB debugging is turned on
  2. Open the “C:\android-sdk-windows\platform-tools” folder
  3. Open a command prompt
    1. Press and hold the shift key and right click in the folder window
    2. Select Open Command Window Here
  4. In the command prompt type “adb restore C:\backup\mybackup.ab” and press Enter
  5. When the phone shows the Full restore screen, type in the password you created in the Backup your phone with ADB section
    1. This may take several minutes, be patient
  6. You have now restored your phone

More great ADB info

Copkay's xda-developers.com Thread
Copkay has an excellent thread at XDA-Developers.com on how to backup with ADB.  
If you haven't checked it out, you definitively should!

Fish1552's galaxynexusforum.com Thread
fish1552 has a very nice thread at GalaxyNexusForum.com on the basics of ADB commands