How do you trace a short circuit that's draining the battery?

U disconnect the NEGATIVE battery cable & put a 12Volt test light IN BETWEEN the cable & battery post(connection) THen U start pulling fuses un- till the light goes off MAKE SURE U have ALL switches & doors shut because (doors-radio-etc) will turn on the test light.IF IT still doesn't go out after all the fuses have been pulled-THE problem is in a HARD WIRED CIRCUIT like the HEADLIGHTS etc.