Dont forget the obvious...
Dont forget the usual basic checks....
The seller - Make sure you gain entry to the house its registered to (ask to use the toilet), ask him/her questions about what repair work its had done, assess whether the seller is likely to have thrashed it everywhere or skipped services etc.
Past history -
service records (check for
service indicator), MOT's, tax discs - the more info the better - make sure it all adds up
V5 - check details such as engine codes, VIN numbers, gearbox codes, paint colour etc.
Mechanical condition - Tyres, brakes, shocks, knocks, rattles, clicking noise on full lock, smoke on start up, smoke while driving (get a mate to tail you if poss), white gunk under the oil filler cap, oil level and condition, state of pipes and wiring in engine bay.
Exterior - Check all panel gaps are smooth and even, look along the sides to check for dents or ill fitting panels, check paint for signs of orange peeling (cheap respray), check all black plastics/rubbers for signs of overspray
Interior - marks, scratches, tears, shards of glass under seats, bubbling on the dashboard due to heat etc.
Electrical - air con, heater, lights, dash, wipers front and rear, horn, the whole lot!
On a ramp/over a pit - check chassis rails for straightness, cabin floor for buckles/creases, exhaust/cat condition, check for oil or coolant leaks, impact damage due to bottoming out, obvious weld seams etc.
The this is by no means a complete list, as it goes on and on really!
Dont be afraid to have a good poke and a prod all over the car. Remember, your the one whos parting with your hard earned, so dont be shy or embarrassed!
Test drive as many as possible. Get a feel for the model, and keep alert for quirky individual behaviour.
These are fast cars to start, so dont be blindsided by the fact it goes like smelly stuff off a shovel!
Ultimately, if in doubt, step away.
Hope this helps, and happy motoring,
Dan