The following instructions and charts are copied with permission from Norman Koren's website. Pictures on this site are edited on a gamma=2.2 monitor.

Gamma and black level chart
The chart on the right enables you to set the black level (brightness) and estimate display gamma over a range of 1 to 3 with precison better than ±0.1. The gamma pattern is on the left; the black level pattern is on the right. Before using the chart, the monitor should be turned for on at least 15 minutes (30 preferred).

Gamma  is estimated by locating the position where the average luminance across the gamma pattern is constant. The corresponding gamma is shown on the left. You should be far enough from your monitor so the line pattern is not clearly visible. The example below shows what to look for. The solid areas are calculated from the equation,
pixel level = 255*luminance(1/gamma) ;    luminance = 0.5.
What to look for
(for Gamma = 2.0)
  This chart features gradual density changes along horizontal scan lines (thus eliminating risetime problems). It allows more precise gamma estimation than most traditional charts. I encourage you to download it and check it occasionally.

Your monitor's gamma should be 2.2 or 1.8.

2.2 is recommended for Windows, the Internet sRGB color space, and the popular Adobe RGB (1998) color space. 1.8 is the standard for the Macintosh and prepress file interchange. I aim for gamma = 2.2. Most laptop LCD screens are poorly suited for critical image editing because gamma is extremely sensitive to viewing angle.

Black level (brightness) Your monitor's brightness control (which should actually be called black level) can be adjusted using the mostly black pattern on the right side of the chart. This pattern contains two dark gray vertical bars, A and B, which increase in luminance with increasing gamma. (If you can't see them, your black level is way low.) The left bar (A) should be just above the threshold of visibility opposite your chosen gamma (2.2 or 1.8)-- it should be invisible where gamma is lower by about 0.3. The right bar (B) should be distinctly visible: brighter than (A), but still very dark. [March 31, 2004: I checked the pattern on a well-calibrated Sony Artisan monitor at PremierScan. Left bar (A) disappeared at about 0.4 units below the gamma setting.]

There is considerable interaction between the brightness and gamma settings-- increasing brightness decreases gamma-- so you may have to go back and forth two or three times. There is less interaction between Contrast and gamma. The vertical bars correspond to normalized luminances of 0.002 and 0.006 at the specified gamma.