You may be wondering if you calibrated your monitor correctly. There are two ways to check whether or not you correctly calibrated your monitor. The software that comes with your colorimeter might have a feature to validate your calibration. The lower-tiered hardware/software solutions usually don't have this feature though. Another way to validate your calibration is to use test images and test charts. This option uses your subjective eye and mind though, so it isn't very accurate.

Calibrating and profiling your monitor is an important process to do regularly (every 2 - 4 weeks). This will ensure you are seeing colors on your monitor accurately. It will also help to ensure others see your images in the way you intend on many different devices.

You can profile other devices: your printer, your scanner, your projector, etc. Your monitor is the most important device to calibrate and profile. Many people can get away with calibrating and profiling monitors only, but some professionals may want to profile other devices. X-Rite makes a product called ColorMunki Photo which will calibrate your monitor and profile your printer and projector. If you have an inkjet printer, the included ICC profiles are generally pretty good and you can generally get good results without profiling it. Some people may want to profile their inkjet printer for optimal results though. Laser printers are unstable in their specifications and vary greatly. They should be calibrated and profiled regularly.

Color management can be pretty complex. Calibrating and profiling devices is a very small part of color management. With all the platforms and devices out there, getting accurate colors can be difficult. Calibrating and profiling your monitor is something simple to do and can help a lot though. I recommend that you do it and do it often.