Have a good read of the buyers guide.
2 things I've since learnt after buying mine were to have a look at the aux & air con belts, they are early visable in the engine bay, had I noticed I would have haggled more on the price of mine.
Also, and this is a biggie, check that the tyres not only have a decent tread but are a decent brand (have a read on some of the tyre threads on this forum for "preferred" tyres for the Z). Mine had brand new tyres all round when I bought the car, I checked the depth on the tyres but didnt consider checking they were a good brand, I'll need to spend the best part of £800 getting new tyres when I can. For now I can't enjoy the car as much as I'd like.
You're certainly in the right place to research your potential purchase.