turning mechanism

i am trying to build a rf controlled vehicle(toy car). how can i make the car turn left or right, i mean is there separate gear box or should i buy one toy rip it off and use it for my car. i cant understand the mechanism to make it turn left or right. can anyone help me with this.... i have this doubt in the line follower also....

For a line follower you normally have two motors connected to the two back wheels and turn by running them at different speeds. A good gearbox to use is the Tamiya dual one.

Mike.

i build robot mobile with wheel. but i have problem .
how construction robot can run on the stair?. how many wheel?
can anyone help me...