Check out Iwasaki-san's bristlebot-mod-mod He uses a transistor to amplify the vibrations.
Step 1: Ingredients
Of course you could use a transistor, light sensor, and a few resistors, but you can't beat the simplicity of using a learning sensor, plus the fact that you can easily calibrate it on the fly.
Step 2: Circuit Diagram
Step 3: Motor & Learning Sensor
Finally, now attach the motor wires to the diodes's pins. Unless your motor specifies it, it doesn't matter which wire is connected to which pin.