There are two things you need to do to your screen:-
Why do you do this? Well if your screen isn't setup right then your images wont look correct and you may find you're editing out problems that are not due to the image quality but due to screen problems. The result is you may make them look good on your screen but they wont print out correctly. Just think - if your screen has a tendency to always show your pictures a little dark and reddish then you could correct this to look good on screen. The resulting prints may then look too bright and lacking in red tones. Also if the program can't translate the colour data correctly then again the images may look on odd on screen.
Don't assume that your display is set right straight out of the box. Many LCD screens these days are setup way to bright and high a contrast setting. I've had to reduce mine but as much as 50% to get it correct. If you want a quick test to see how well your screen is look at the image below. You should be able to count 21 different tones in going from Black to White.
How to Calibrate and Profile?
Sorry but this is going to cost you some money! To do this correctly you need to buy something which has the technical name of a Colourimeter. Basically its a piece of hardware that actually measures the output from your display. You run some software that comes with it, which guides you through adjusting the brightness, contrast, colours etc of your display while it measures the screen output. Once this is done those details are stored in a profile for your display and are loaded every time you start your PC.
Do a Google Search for items like a Gretag Huey or Eye-One Display 2 or Spyder. They will set you back a few tens of pounds or dollars but are very worth while.
What about the Adobe Gamma Wizard?.
Chances are you may have heard about the Adobe Gamma Wizard which is a a free piece of software that could be used to setup your display. Like most things in life 'there ain't know such think as a free lunch'.
Firstly the Adobe Gamma Wizard only Calibrates your display and you have to 'eye-ball' the settings to judge when you think they are right.
Secondly, as display technology has advanced this product is really past it's 'sell by date'. In other words it's not very good with modern LCD screens ( nor high resolution CRTs). In some cases, as I've experienced it produces worse results than the manufacturers defaults.
By all means give it a try but I don't recommend it. For instructions on how to use it look here.