The Leviton 6681 is a push-button rotary-type incandescent dimmer with 600Watt capacity
If you have incandescent bulbs, the dimmer should work.
If the dimmer has different color wires, try reversing the wires.
If the dimmer replaced a 3-way switch, then this is not the right dimmer.
If you have compact florescent bulbs, you need a dimmer that also dims florescent.
http://www.google.com/products/catalogLink shows the Leviton 6673 incandescent and florescent dimmer
But you also need dimmable compact florescent bulbs.
http://www.amazon.com/DIMMABLE-COMPACT-FLUORESCENT-LIGHT-SPIRAL/dp/B0014B84ZM