Starting with the community's five most-upvoted checks from past threads:
- VIN report before the test drive — cheapest insurance there is.
- Cold start with your hand on the fender: knocks and misfires hide from warm engines.
- Photograph the buyer's order before you sign anything, every time.
- Tire date codes — four matching recent tires is a caretaker's signature.
- If the seller rushes you, the car has a reason. Walk.
Add yours below; best entries get merged into this post.