Matty - unless you have consistent ambience in your room lighting, don't worry about it too much. Proper monitor calibration is ideally set up in conditions where the surrounding light temperature is set to 5,000 deg kelvin - such as that which you get in a light booth at a photographic studio or ad agency. Without consistent room lighting your are venturing into a world of frustration. I worked for years in these places and calibration was a time-consuming and constant process. Of course, no one here is going to go to this extent because you aren't looking for perfect skin tones on press for a high-quality glossy magazine ad campaign.
We also have LCD monitors these days, not CRT so much any more. LCD panels are not really that great for their calibration ability unless you go for the far more expensive models. Given that, as Leon says, use the tools that Photoshop's Adobe Gamma provides if really want to, but you really need a hardware calibration device to physically measure your monitor's colour output if you want to match it to a printers.
Here's a good little explanation:
http://www.drycreekphoto.com/Learn/m...alibration.htm