. . .more on Formulas 

 
TP = (HI + LO + CL) / 3
    TP stands for Typical Price

MATP = MA(TP, n)
    n = CCI Period
    MATP stands for Moving Average (Simple) of Typical Price

    where n = CCI Period
    MDTP stands for Mean Deviation of Typical Price
 
CCI = (TP - MATP) / (MDTP * 0.015)

Modified CCI
When "Modified CCI" is checked, the Typical Price is calculated differently, as seen below.  Otherwise, the calculations are identical.

TP = (Max(HI,n) + Min(LO,n) + CL) / 3
    n = CCI Period
    TP stands for Typical Price

. . . more on Charts 

Above is a Daily Candlestick Chart of the Microsoft Corporation (MSFT).  The blue line in the lower window pane represents the CCI using the preferences seen in the window below.

. . . more on Preferences 

• CCI Period - Period used in the CCI calculations above.

• Reference Line (1, 2) - Levels at which to draw horizontal reference lines.

• Modified CCI - Dictates the method used for calculating "Typical Price".  (See "Formula" section above.)

• Smoothed CCI - Check this if you would like the CCI line smoothed.

• Smoothing Period - Smoothing period used only if "Smoothed CCI" is checked

• Smoothing Type - Smoothing type used only if "Smoothed CCI" is checked

• Draw As - Options for drawing the CCI as a continuous or connected line, or a hollow, solid, or custom historogram.

• Line Color - Color and style of the CCI line in the chart.

Buy Signal
CCI > 100 AND CCI.1 <= 100

Sell Signal
CCI < -100 AND CCI.1 >= -100

A more aggressive use of the CCI indicator dictates entering positions when the index crosses the 0 line.  This method helps incorporate the early part of a new move.  When the CCI crosses above the 0 line from negative territory, this is a bullish signal.  When the CCI crosses below the 0 line from positive territory, this is a bearish signal.  The following scans represent this strategy.

Buy Signal
CCI > 0 AND CCI.1 <= 0

Sell Signal
CCI < 0 AND CCI.1 >= 0

Some traders actually use this indicator in the exact opposite way. They interpret levels above 100 as overbought regions and bearish signals, and levels below -100 as oversold regions and bullish signals.
 

CCI > 100 AND CCI.1 <= 100

And to liquidate this position when the CCI crosses back below the 100 line:

CCI < 100 AND CCI.1 >= 100

Other strategies involving CCI can be found in the description above.