Wiring a Lambda/O2 sensor...

[spoodler]

Can anyone please tell me how to check the wiring on a car with a four wire sensor? It's not the wiring on the sensor that I need to check but the wiring on the car. I know that one will be earth, one sensor and two heater. I have bought a new sensor but wish to confirm the wiring before fitting (rather than just replace like for like) as I think the previous owner wired a replacement sensor incorrectly.
Haynes type manuals aren't available and wiring diagrams/colour coding available on the 'net contradict each other.
Thanks.

[spoodler]

Thanks for the reply.
The previous owner had fitted cheap replacement sensors by splicing into the loom, therefore I can't just plug in my nice shiny new one. The actual connecting of the sensor/making up a plug isn't a problem but I need to confirm which wire is which before I damage my expensive new one...
The earth should be easy enough to work out. Can anybody advise how to tell the heater wires from the sensor wire please?
Thanks.