Difficulty Level: very easy
If you are running the latest Firmware on the RaspberryPi your Pi is able and should automatically boot from USB. If for some reason it does not, here is how to change the boot order manually.
Use the command line and make sure that you run the latest EEPROM Version by typing sudo
=> How to Update EEPROM
If there are no updates type
sudo raspi-config and follow the steps below.