Analogue cameras send composite video over coaxial cables, which are available very cheaply.

Two different types of connectors are found on composite video cables:

BNC

Commonly found on analogue CCTV cameras and TV aerial sockets.
 

RCA

Commonly found on video input hardware and other consumer electronics.
 

Check the connection sockets offered by the analogue cameras and video input hardware you intend to use, so that you can choose cables with the appropriate connectors at each end.

If your cables have the wrong connectors, this can be easily corrected with the use of a small adapter, available from many electronics retailers.

Many RCA cables and adapters intended for CCTV only have one plug, which is all that is necessary for carrying video. RCA cables with three plugs use one plug (usually yellow) for video, and the other two (usually red and white) for audio.