As private sellers are under no obligation to reveal a car's history, or offer proof of any checks, the onus is very much on the buyer to determine a car's past.
The first stage of this process is conducted over the phone - and if you get it right, it can save a lot of hassle and wasted time.
Questions you must ask:
How long have they owned the car? Have they owned it from new? If not, how many previous owners are there? If the number plate is visible from the advert's image, you can find out the vehicle identity with a free Auto Trader Vehicle Check.
Why are they selling it?
What is the mileage? What features does the car have? In their opinion, what sort of condition is it in?
Is there an outstanding finance or hire purchase agreement?
Are there any service records, bills, old MOTs? (Use the latter to check mileage).
Has it been involved in any accident damage, and if so, which parts were damaged? Where was it repaired? Are the repairs guaranteed?
Have they replaced anything on it recently? Has it been modified in any way?
Price should be negotiable - are they open to reasonable and fair offers? Compare similar car model prices by reading our setting the price page.
Things you should never do:
Arranging to meet in a 'mutual' location, such as a pub car park. Why doesn't the seller want to reveal their address? Are they making sure you have no comeback?
Not noticing mobile numbers; they're commonplace nowadays, but why should someone not want to back it up with a land-line number?
Miss a trader or canvasser in disguise. The classic opener on the telephone is to ask if "the car" is still for sale - a "which one?" response is a dead give-away. Traders sometimes sell dodgy motors 'in disguise', thus avoid legal obligations to repair problems.