Ground straps on a 2000 Sunfire

I was wondering if someone could tell me where the body and chassis grounds are on the Sunfire coupe body style before I crawl under the car and start looking.The stereo in the car is acting strange in that it will only work on one speaker,drivers door,when the weather is wet but as soon as the sun comes out they all seem to come back slowly but surely starting with the passenger door one and then the rears.The car sat all winter not being used and I'm wondering if a ground is not getting the connection it should or perhaps someone might shed some light as to what else might be causing the problem.