You'll need an amp meter (mulit-meter), but it's fairly easy if it's one of the fused devices.
Turn the car off and remove the key. (Remember, there's a theft warning buzzer and it draws current!!) Now remove the Negative battery cable and place the multi-meter on the highest reading you can (usually 10 amps). Now hook one side of the amp meter (multi-meter) to the battery, and the other side to the unhooked negative battery cable. See what the reading is. If it's 0, then go to the next lowest setting on the meter. Continue until you get to the lowest setting on the meter OR you start getting readings. If you get a reading, you do indeed have a drain. Now remove one fust at a time from the fuse block until the meter goes to 0. What ever fues makes the meter go to 0, then this is the device(s) causing your problems. Now you have to find out what the problem is with that device.
If it's NONE of the fuses (you still get a reading with all the fuses removed), then you have a problem through the charging circuit or starting circuit. But let's see where this gets you first.
Remember, dome lights, trunk lights, underhood lights, etc... draw current so take that into consideration. Even clocks and radio memory circuits!!