I have been to the car store four times and each time they tell me that the battery is good. A few of the cold-cranking amps (maybe at 50 or so, I don't remember the exact amount) are gone otherwise it just needs a good charge. Despite that information, my car's battery is found low enough that I can't start the car way too often ('98 Chevy Malibu). The battery is around 3 or so years old. I can charge it and things work for a while. One battery test they did also tested the alternator and that seemed to be okay.
The last time I was there, they suggested maybe something like a radio or computer is starting to suck battery when it isn't supposed to. I have a multi-meter. Where should I start to diagnose this myself so I don't have to pay an arm-and-a-leg for diagnosis. The only accessory I use is an iPod/iPhone radio transmitter. I realize it does use some power and doesn't help, but I have been using that for at least 3 years now and never had problems before. Any other ideas?