Make sure it has full Service History. Lots of L322s are expensive throughout their lives, so many owners have a stack of repair bills. It's re-assuring to see thes, as you can see if the car has been looked after.
Check service history, and phone the dealers in the book to confirm servicing was done.
Phone LR Head Office with Chassis No, and ask what the spec was, when the car was built. This will give you an idea of exactly what spec the car is, and what was added later. (bear in mind, some accessories are fitted at the dealers, and so are not on build sheet.)
Make sure if it is a vogue, then it says Vogue on V5. Some were HSE spec, but in the rush when RR was released, the dealers made some HSE's up to Vogue-ish spec... I saw one with all vogue kit (heated rear seats, heated steering wheel, sat nav, tv) but not the Vogue Seats. (the vogue seats have a strange shaped heatrest, unlike th HSE ones.)
Check tow bar, to see if the car has been used to tow much. Ideal situation is a shiny tow bar still in its wrapper, because the owner never used it!
Find out what the owner used it for, and try to gauge whether or not they were likely to have maintained the car....
Thats all I can think of for now...