Remote controls (robotics)?

How can you connect a remote control of any sort to a reciever/transmitter.

I am make a robot from scratch and need to make sure how to connect a remote to it before I start.

Do you have to make sure the remote and receiver/transmitter are the same MHZ.

I have done a test on 2 remote control cars. 1 car had a 27 MHZ receiver/transmitter and I didn't use the original remote it came with, instead I used a different 27MHZ remote and it didn't make the car move.

Can someone help.