Controlling a motor with a relay. The PDF linked below will guide you through the following:
1. Learn the nomenclature for switches / relays
2. Set up a basic relay circuit to turn on and off the coil / switch
3. Use a relay to turn on and off a motor
4. Use an Arduino to control a relay circuit with a transistor
http://jasonkrugman.com/classes/documents/relaysAndMotors.pdf
