...by adding the following tag line to your email program signature:
Before you print this or other documents, please consider the impact on the environment
One little thing that I think we can all do is make a concerted effort to use fewer resources. A simple little change would be to save your emails electronically instead of printing them out.
Below is a little screenshot of the signature that I've added to my email messages. Consider giving this a shot in your email program. Perhaps you'll encourage a few others to think twice before they indiscriminately hit the print button!