GM Service Manual Online
For 1990-2009 cars only

Parking Your Vehicle/Key Removal Manual Transmission

Before leaving a manual transmission vehicle, fully press the clutch pedal in, move the shift lever into REVERSE (R), and firmly apply the parking brake. Once the shift lever has been placed in REVERSE (R) with the clutch pedal pressed in, you can turn the ignition key to LOCK, remove the key, and release the clutch.