Swap the bulbs you use 3+ hours a day for ENERGY STAR LEDs
Added
Start with the lights that stay on longest, since DOE suggests replacing bulbs lit three or more hours a day first, then swap the rest as they burn out. Pick ENERGY STAR-qualified LEDs, and dimmer-compatible ones for fixtures on dimmer switches.
The result
Result: DOE: LEDs use at least 75 percent less energy than incandescent bulbs and last 25 times longer.
Source
U.S. Department of Energy: Guide to Energy Efficient Lighting (opens the original source in a new tab). Check it for the latest numbers before you act.