All you are doing is changing settings that the display driver uses so it isn't permanent by any means.
First step would be to download a test image and see how it looks. Do a google for "PDI test image" and you'll find one. These are used in photographic competitions to calibrate a projector used to display digital images.
It should include a grey scale from black to white and the first step is to check that it looks uniform and all steps in the scale are visible. You can adjust brightness, contrast and gamma to ensure this.
Secondly you need to look at the colours and see how these look. This starts to get more tricky and subjective but try getting an accurate print and comparing it with the same file on the monitor, under natural light if possible. Try to assess if the colours look too warm or too cold, over or under-saturated or have a "colour cast" and adjust the display as required using the settings in your display driver (usually in the "advanced section" under "colour management" or similar).
You can also get relatively cheap (sub-£100) colorimeters to automatically calibrate your monitor. This might be worth a look if accuracy of images is important to you. These essentially measure the accuracy of the light from the monitor and automatically change the settings.
Kevin