The PRO (Professional Referee Organization) which assigns referees to professional soccer matches in MLS, USL, NASL, NWSL, etc. has released a training video they use for their assistant referees.

See how many you can get right: (Write down your answers. The answers are revealed half-way through as each clip is repeated with a pause at the time of the decision.)

Source:  http://www.proreferees.com/news-offside-test–pro-assistant-referee-training-camp.php