Useful tip if your "check engine" light is on
Don't go to a garage, which will charge you $80-150 to diagnose it. Instead, go to Autozone, which will read the on-board computer's diagnostic code. Then, go to a repair shop if it's something that actually matters. This will save you money if it's something dumb like needing to tighten the fuel cap.
ETA: It looks like AAMCO thought of my idea for repair shops to offer free OBD scans. They'll do the OBD scan, and then fix whatever's wrong.