Tire Pressure: Having proper tire pressure is very important both on the way up to the mountains as well as during "spirited" driving. Tire pressure may be altered just before a run in order to change vehicle handling characteristics as well as for grip/tire wear between the trip up and the actual run itself.
Check tire wear: You don't want to go up to the touge with belts showing on your tires. You should always have ample tread.
Brakes: Check pad level and for even wear, aswell as brake lines for leaks or cracking.
Oil Level: This goes with out saying and should be checked regularly on any car. But as a precaution this should be double checked before the trip up aswell as before a run and before the trip home.
Extras: Have extra fluids on hand...power steering, brake & clutch, transmission, oil, water and/or antifreeze.
Tools: Some key tools for your particular car are wise to bring.
Open ended wrenches, socket set, screwdrivers, pliers, flashlight, and of course ZIPTIES and DUCT TAPE.
Torque: Check the torque on parts that you've recently added...parts falling off on touge=not good!
Other Items:
-Check all fluids, power steering, brakes & clutch, coolant, washer, etc
-Make sure to have enough gas to finish the run
-Fire Extinguisher
-Bring walkie talkies to communicate (cellphones typically suck in the mountains...except VERIZON FTW)
-Cash (it's king) Just in case!
-Remove loose items from vehicle
-Maps/GPS
-Camera
You never know when you may have a problem up there and gotta get it fixed to head back.