All the above are wise words but my best experience at the ring was meeting the German guy with the ring vtec mini. We made contact with him before we left and he and his mates met us there, then he took us out in his mini estate.
What an experience!
You tube clips:
Ring Mini. The fast edit. Nurburgring. - YouTube
He is a nice bloke and does have a website, alternatively if your interested, PM me and I can give you his mobile number. He knows the track like the back of his hand and is a great driver.
Spa is great, and the best lunch I have ever had at any track!