Have you ever gotten a softcopy of an image that looked wonderful on your computer but looked terrible when printed? Have you ever gotten different "looks" or "colors" of the same picture file when printed on different printers? Did a friend's wedding gown looked absolutely pristine and white on the computer screen and then looked yellowish in printed form. Have you ever wondered why that happened? A major factor is color calibration.
Each of our devices - our cameras, our computers, our printers - have different profiles and some of that we even adjust ourselves like contrast, saturation,etc...so what you see on your computer monitor may not be the same thing that your printer sees when it tries to print your photos since it has a different profile.
Professional photographers go through a process of calibrating their monitors, their cameras and their printers (or take considerable time to acquire the profile of the printer/paper that their lab uses). This ensures that what they see on their monitors will look EXACTLY the same way when printed and can reproduce the same image with consistent color.
The best way to calibrate your monitor is via a dedicated hardware and there is a lot that the industry has to offer. There are products from pantone or data color that I am using. I am particularly liking the spyder 3 elite for most of my work now with a gamma setting of 2.2 and temp of 6500K (typically daylight temp).
I also use a colorchecker in some of my sessions where color is critical and it is simple to use. Ensure you have one image of the checker for the same lighting condition, create a dng image with that image and then load and apply it like a recipe to other images in the same lighting condition. It saves me a TON of time although it is not that useful if you don't calibrate your monitor as well.
If you want more of the science along with the products - you can go to colour confidence