Right-click in a blank space anywhere on your Desktop, select Change Desktop Background and in the resulting dialogue box click on the Visual Effects tab.
Select Extra then click Close.
This will enable the stock visual effects. To be able to control and change the effects you'll need to install the Compiz Settings Manager.
Open a Terminal (Applications > Accessories > Terminal) and type (or copy/paste) the following code;
|sudo apt-get install simple-ccsm|
You'll now find the Settings Manager in System > Preferences under the name of CompizConfig Settings Manager.
Have a play round with it and customise the effects to your heart's content!
Check back in a little while for a Tutorial on Advanced Desktop Effects – such as the Desktop Cube etc.