First, remove the battery - charge it fully, then load test it. If it tests good. Set the battery back in the battery compartment and connect the positive cable. Then run a test light (you can get a cheap one at harbor freight tools) between the negative battery terminal from the car to the negative terminal on the battery (basically complete the circuit with the test light in the middle). If you have a big current draw, the test light will light. If the test light lights up, leave it connected and go to the fuse box and start from the top and remove and install one fuse at a time. Do this until the test light goes out. When the test light goes out, you'll know what circuit your problem is on.
Go here http://www.bbbind.com/free_tsb.html
and look up the wiring diagram. then put the fuse back in and start removing components on that circuit (for example, if the radio is on the same circuit just go down the list of items connected to that circuit and disconnect and reconnect one at a time until the test light goes back off), when it goes off, you have found your source of current draw.
If you start this process and the test light does not light during the first step, you will need a DC Amp Clamp meter to read the smaller current draw (sears has a AMP CLAMP METER that does DC AMPS for around $50). In this case, you would connect both battery terminals (connect positive first), then use the AMP CLAMP on the DC AMP setting to read the current draw and repeat the same process as mentioned above.
Please reply if you have any further questions.
Hope this helps!