how to control 2 12v dc motor using a Raspberry Pi?

I am trying make a Raspberry Pi controlled 3.5 foot robot to move soda around the house and I was wandering what is the best way to control a 12v dc motor using a Raspberry Pi?   Please help me.

You will need a motor controller to run the motors. The control will then take a PWM input from your Pi or Arduino to tell it which way and how fast to run the motors. Be sure that the controller and your Pi/Arduiono share a ground connection.
You can get plugin interface cards for the Pi, but you can also use an Arduino, and a motor shield on that, to talk over USB to the Pi.