If you are limited on what you have for testing tools, you can use this method. Unhook your battery negative cable and install a test light between your negative post and negative cable. If the test light comes on and everything is off ( all accesories, lights, etc.) then something is drawing from your battery. To find out where the draw is coming from, pull fuses one by one and when the test light goes out you have found the constant draw. Some components may be drawing from your battery a small amount such as audio. Hope this helps out.