Where to find the VIN on a vehicle
The VIN is on the vehicle in at least two places and on most of its papers. If two of them disagree, go by the one stamped or riveted to the vehicle.
On a car or a light truck
At the bottom of the windshield on the driver's side, on a small plate on top of the dash. It is read from outside, standing by the driver's door and looking down through the glass. Vehicles built for the United States and Canada have it there.
On the driver's door jamb or the edge of the driver's door, on the label that also gives the date of manufacture and the weight ratings.
Stamped into the body or the frame. Common places are the firewall at the back of the engine bay, the top of a front strut tower, the floor beside a front seat, and a frame rail on a truck.
On the papers
On the ownership or registration, on the insurance card, and on the title where one is issued. A bill of sale and most service invoices carry it too.
On a motorcycle, a trailer or a heavy truck
A motorcycle has it stamped on the steering neck, behind the headlight, and often on a label on the frame.
A trailer has it on a plate or label near the front on the left side, usually on the tongue or the frame.
A heavy truck has it on the label on the driver's door jamb and stamped on a frame rail.
Reading it without mistakes
A VIN never contains the letters I, O or Q. If you read one of those, it is the digit 1 or 0.
The pairs most often mixed up are S and 5, B and 8, Z and 2, G and 6, D and 0, U and V, and L and 1. When a VIN typed here fails its check digit, the result page offers the VINs that pass the check and differ by one such swap.
A VIN from before the 1981 model year can be shorter than 17 characters and follows its manufacturer's own layout. This site decodes 17-character VINs only.