Via System Preferences

1. Launch System Preferences
2. Click on Dashboard and Expose

Via Dashboard (shown to the right)

1. Click and hold on the Dashboard icon in the Dock.
2. Clcik on Dashboard Preferences in the pop up menu

Both methods will take you to the Dashboard and Expose area within Mac OS X System Preferences.




Shortcut Key (Hot Key)
As you can see, F12 is the default hot key or shortcut to launch Dashboard.  You can alter it by clicking on the drop down box and select an alternate key.  You can disable Dashboard launches from the keyboard by selecting the dash underneath F13.



Active Screen Corner
You have the option to set an Active Screen Corner, a corner on the screen that when clicked with the mouse will launch Dashboard.