Here's the proper way to test for drains.
WIth the car off, you typically want less than a 1A draw on the battery. Obviously the less the better, but most cars hover under 1A.
You need a multi-meter that has the ability to measure Amps in DC voltage. You need to remove the positive wire from the battery and hook the meter up in series with the cable and battery post. One wire to the post, the other to the wire.
It will now measure current draw.
If you have under the 1A, then it's a weak battery. Once they die, they are never the same and will drain very quickly if the car sits. The key is to never let the battery drain down ever. If it does, it will never hold the charge the same again.
If you have more than an amp, time to start pulling fuses and see if you can isolate what circuit is drawing.
Once you isolate a certain fuse, you can track down some wiring diagrams and see what it powers. If it's a lighting circuit, it could be a shorted bulb, or a bad socket or some other fault. Could be a wire that rubbed on the metal and is shorting to ground or something like that.
