Arduino DIY motor shield

polishdude20:
Lastly, would I even NEED an H-bridge to make motors JUST move forward like in a line following robot?

You only want an h-bridge if you intend to reverse the direction of the motor; if you don't need this ability, then a simple NPN transistor or N-channel mosfet (plus a diode, and maybe a resistor) is all that would be needed.