Do not listen to this, this is uninformed ramblings, I may update it with correct information for modern displays (LCD) at some point.
I have for some time struggled with my monitors gamma, and have finally found a lasting solution:
EDIT: Oh yes, make sure your CRT monitor has been on for quite a while, half an hour to an hour. TFT/LCD only a minute or two. Ortherwise the screen will still be in it's startup process and display a different gamma.
On this site there are some very good gamma checkers, and should be used as a point of reference throughout the tutorial:
The site's other information is really quite unimportant, what we need to focus on is the gamma info.
For the standard PC monitor you should aim for a gamma of 2.2, Mac monitors 1.8
Step One: Getting you monitors color grading set to Equal energy
It is important that your monitor has a whitepoint that is as neutral as possible when fiddling with software correction, otherwise your monitor will be corrected twice. This of course assumes that whatever gamma software you use also has a whitepoint setting. Also, usually on a screen, 65 is too red and 93 too blue.
In your monitors color settings, put
red to 100%, green to 94% and blue to 86%. Or something equivalent.
EDIT: Duh, what the hell was I thinking? Just put the darn things to equal values: e.g. "60%, 60%, 60%"
Step Two: Software correction
First, you need the right software. If you have Photoshop, Adobe Gamma can be used. But I recommend WiziWYG .
Follow the steps your software gives you to acheive correct brightness/contrast scales. Some monitors contrast setting does not affect gamma. In that case, I'd match the black level scales to the white ones.
When you reach the portion where you have to match three gamma readers, - that is, patterns of stripes and solids - the point is to detect the linear gamma setting for your monitor, wich is the setting that yields a 1.0
Adjust the settings until photoscientia's scale has the 1.0 readout grayed out as much as possible, try several times if nessecary. http://www.photoscientia.co.uk/Usingmira.htm#Gamma
Now, select the remaining settings that fits you, but make sure that you keep the whitepoint to 6500 or D65, and the gamma to 2.2 - 1.8 for Mac monitors if you are using one.
Depending on your ability to determine linear gamma and brightness/contrast levels, your screen should now look correct. Check it out with photoscientia to make sure, the point is for the target pattern to be as grey as possible at this point.
You may have to try gamma correcting several times to get the right results.
You can also use your video control panel (ATI CCC, Tray Tools, Nvidia stuff) to the same effect. Although often with less accuracy.