Makes it drive forward (clockwise) and switching it to pos - neg and neg - pos drives it back (counter clockwise). To control it i actually have to push 12v DC power to get it to turn one way or another. So how would I do this without burning up my board?
Look up "H bridge", that's a circuit you used to swap the + and - for this sort of motor control. The Arduino drives the gates/bases of transistors and they switch the 12v, so the Arduino never sees the high voltage.
A motor-control shield will do this for you.
Rob