Well noises and such should be pretty obvious, your typical gear whine, fluid leaks, poor fitting t-tops and signs of leaks (assuming its a t-top car), melted front marker lights, poor operating headlight motors with stripped teeth on the plastic gear that operates them, and I'm sure you can handle most of the basic mechanical checks. If I can think of anything else I'll post it. Get the VIN and I'll check its history from GM.
Also inspect the seams inside the hatch where the quater panels attach to the unibody, those were known to seperate on some cars.