Connecting an analog TV, a DTV tuner, and a DVD player.

I have a question to ask those of you who are good with connecting electronics.
I have an analog TV, a DTV tuner, and a DVD player. How do I connect the three of them to make the switch between watching TV and watching DVD using the TV set?

I can connect the TV to DVD player using RCA cable fine, or TV to DTV tuner using RCA cable fine. But how do I connect them together?

I do not need to record anything. Just want simple playing of DVDs and watching TV.

Many, many thanks,