1997 gsr.

1. new battery.
2. new alternator.
3. new battery pos/neg cables.

The battery keeps dying if i let it sit for 1 or more days without running the car. So basically i have something draining the battery, the only things i can think of is the alarm (4 years old haven't had a problem until now), the starter or maybe my amp but i've replaced the amp.

Any ideas as to what's causing my battery to lose charge? if so, how do i go about checking?

Thanks in advance.