When checking for an electrical draw, use an amp meter(common on most volt meters). First, disconnect the posative battery cable, then connect your amp meter between the battery cable and the battery terminal... this completes the circuit through the meter and will show you how many amps are drawing on the battery. MAKE SURE all accessories are off and doors are closed(ie: no extra draws on battery).

NOW, you are looking for a reading that is less than .10 or one tenth of an amp... if it is more, start pulling fuses and tracking it down(a power distribution wiring diagram is very helpful when you locate the fuse causing the draw). Start with the mega fuses and narrow down the circuit, once you found the circuit get a diagram that shows what fuses/accessories run off of it.