Other important issues you'll need to consider before installing a new concrete driveway include accommodating  in-ground utilities, such as main water lines, electrical lines, and sprinkler pipes, and allowing for enough walk-around room. See these design tips from landscape architect Scott Cohen:

Driveway Walk-About Space  

Planning for Utilities & Approaches 

Before installing a new concrete driveway, the first decision your clients will need to make, before choosing a color or decorative finish, is how large to make it. What is the best length and width? Do they want a single or two-lane driveway? Do they want to include a turnaround area to allow them to back up a car? Or how about a circular driveway, so they don't have to back up at all? To help your clients make these decisions, here are some guidelines for the appropriate dimensions for all these driveway types. Before finalizing your design, however, be sure to check the driveway construction requirements of your local building code.

Two-lane driveway

Single-lane plan

Double-lane driveway
Make a minimum of 20x20 feet; 20x24 feet is preferred.

Circular plan

Driveway with turnaround