Notes, notes, notes. You spend countless dollars and tireless nights setting your car up for track day fun. But how will you know if all the money and time was actually worth it? Simple and easy to follow setup sheets can mean in 2 years time when you can't remember if you were on Hoosier A6s or A7s, you refer to your handy dandy notebook and know for certain you were on R888s, doh!
Author Ross Bently's various books are excellent sources for learning the ins-and-outs of navigating a racetrack. If you haven't read one of his books, we highly recommend them.