Color management is an often neglected or misunderstood topic but a very important one. Whenever you are editing images on your computer for printing, sending the images to a print house or for web use, you need to make sure that your color management between different devices are taken good care of. Specific colour profiles are needed for each device such as your screen or printer. By using a calibrated and profiled screen of good standard you are more likely to achieve results of highest quality. To start with, it is important to choose a screen that, after calibration, is able to display your images as accurate as possible. Most high end screens are capable of showing almost 100% of the colorspace adobe RGB. Examples of such screens are Eizo Coloredge series or Nec spectra view. An important characteristic of these high end screens are that they present an even illumination across the screen surface. Furthermore, on a good screen you should be able to see increments of the darkest values and also differences in the lightest values (se pictures below of blackpoint and whithepoint).
Use the below image with white background and squares with decreasing values of white, to determine your screens white point. In other words, how good your screen is in differentiating between grey values close to white.
Next step is to profile your screen with a colorimeter that measures specific colours displayed by a program. A profile is created that corrects the presented colours. One state of the art colorimeter is made by a German company called BasiCColor Discus. A common problem with cheap colorimeters is that the membrane gests old after a few years and then it starts to create strange color profiles. When you profile your screen you need to set the colortemperture and strength of illumination. What I usually do is that I match the illumination on my screen to an printed image under a specific viewing condition. The viewing condition that I aim for is a 5000 k daylight source. The screen illumination value that I usually end up with is around candela value of 90cd/m2.