Have you read the information in the link posted by VetteVet?
It covers it.
Or the link posted by 63&64 Bowties? It is the simpliest explaination.
Cliff notes:
*Turn everyswitch off. Everything off.
*Pull battery cable. The reality either one will show the drain from the battery.
*Start pulling fuses, one at a time, checking each time to see if the draw is still pesent. Once it disappears, the last fuse pulled is the circuit that has the issue. Then the real fun begins.
