Assess Your Climate
Winters in northeastern and central North America experience deep frosts, heavy snow and ice. To prevent driveway heaving, you will need a compacted 4-inch base of crushed stone and sand, topped by 4 inches of 4000 psi concrete.
Assess Your Driveway Use
If you own a medium or large pickup truck and two cars, your driveway will be under plenty of pressure when the vehicles are all parked. Dig your driveway 10 inches deep, put in 4 inches of crushed stone, add reinforcing bars across it, and add 2 inches of sand. Use concrete rated at 4500 psi for the driveway surface.
For a Sloped Driveway
On a sloped driveway increase the thickness of the driveway base to 8 inches and the top layer of concrete to 5 inches for stability. Add control joints every 8 feet. Note that 7 percent is considered the maximum safe slope for a stamped concrete driveway.
Source: www.DoItYourself.com