Rendering Lesson #12: How to make windows look tinted.
The important thing is to heavly darken the area that does not have the reflection. This is best shown on the side windows. You must also ever so slightly darken the reflections so they look like relfections on a darker object. To do this in photoshop use the lasso tool and select the area without reflections darken it with the paint brush tool. Turn the opacity and flow way down.
The rear window is a bit trickier. You need to be confident with your airbrushing skills, but this is way easier on the compy than with a real airbrush. No lasso tool here shoot from the hip and darken everything with some quick sweeps of the paint brush tool.