Wikipedia defines color calibration as the ability to measure and/or adjust the color response of a device (input or output) to establish a known relationship to a defined color space.
The most common forms of calibration adjust cameras, scanners, monitors, and printers so a printed copy of a photograph will appear identical to the original file or originating source material.
Before you being to calibrate your devices, you must realize colors are seen differently under different lighting conditions.
Additionally, white balance will also be different in each of the various lighting conditions.
Consequently, there is no calibration system which will make a device look correct and consistent under all conditions.
Color calibration is an integral part to a color managed editing workflow.
There are many different ways to calibrate your devices and several systems you can purchase to help you achieve the best possible color matching between your devices.
However, I wanted to spend my money on lenses and more camera gear, so I came up with the following solution which did not cost anything but about an hour of time.

1. At any hardware store, get two paint chips of the following colors:red, orange, yellow, green, blue, purple, brown, black, white
2. Attach one set of your paint chips to a white piece of paper
3. Attach one set of your paint chips to a black piece of paper
4. You have now created your Original / Source Material
5. Take a photograph of each original in the same room and under the same lighting conditions as your monitor.
   Be sure you take the photo in manual and use the same exposure settings for each photograph.
   
6. Compare the camera LCD screen to your Source Material - adjust LCD screen as necessary
7. Your camera is now calibrated.
   
8. Transfer the images of your source material to your computer - review the images on your monitor and compare to the your camera LCD - adjust your monitor as necessary
9. Your monitor is now calibrated to match your camera
10. Scan your source material to your computer - review on monitor and adjust your scanner settings as necessary
11. Your scanner is now calibrated to match your monitor
12. Send your source material images to your printer - compare to monitor and source material - adjust your printer settings as necessary

To further refine your color calibration, you can now send the images of your source material to the companies who print your photographs for you.
You have the source material to compare their prints with and will now have an excellent way to verify the quality of their colors.