If you've been pursuing digital photography for a time, you've most likely heard of digital targets. These targets are designed to help you achieve a proper exposure and white balance without a lot of fooling around in post-production. They are very handy and I have not been without one on a job in quite some time.
The only real downside to a digital target is the cost, the targets can run you anywhere from $40 to $200 in the stores depending upon the size and configuration you want. Here's a cheap and easy way to make one yourself: