Well for body condition. When u go for inspecting car. Take your honest denter/painter along with you.
Check engine for suspicious noises both on idle and in running.
For mileage. Check the inner condition of car. fenders, Tyres, Cockpit will tell the truth about mileage. You can check it by opening/closing of doors. Door panels, Steering, Brake/clutch/throttle paddle.
Otherwise we cant come to know that car has original mileage on odo or not.