Structure first
Chassis, floors, sills and suspension mounting points decide whether a car is worth restoring. Cosmetics are cheap by comparison, so inspect from underneath before anything else.
Paint and panel evidence
A paint-depth gauge and consistent panel gaps tell you about past accident repair faster than any description. Photograph every finding for the file.
Mechanics and the file together
Compression, oil pressure, cooling and gearbox behaviour should agree with the mileage and invoices. Where they disagree, the file — or the car — needs explaining.