In light of the recent conversations about the use of RAW, I would like to mention something that I've been using since the early days of ACR in Photoshop. Its a free calibration script. You can find it here along with instructions for use
http://fors.net/chromoholics/
You will need a Macbeth color chart for using this.
Calibrating ACR for RAW work ...
Cheers,
rfs