Pose a challenge to employees in a specific location or building to save energy or conserve resources. Refund a percentage of savings back to the employees at the end of the FY. This will encourage employees to be conscious of their energy habits and be creative with savings, rather than blanket mandates from on high for energy savings on one system. Empower workers to control details of their workspace, such as overhead lights vs. desk lamps, HVAC temperature, elevators vs. stairs, etc.
In short: incentivize employees to do the right thing, and they will.