Of course start with the most basic. Get rid of standard light bulbs and switch to compact fluorescent or LED bulbs.
Keep you house warmer in the summer and cooler in the winter. A couple degrees can save a lot of energy.
If you have scalding hot water, turn the temp down! Only keep it as hot as you need it. If you have an old hot water heater, get a new one - one that is well insulated.
Most energy companies offer "green suppliers" It may cost a little bit more, but switch to them. Problem is...right now, even the green suppliers don't have 100% green energy, but at least you'll be showing your support for green energy and encouraging them.
Turn off lights! Even if you're only leaving the room for a minute. We always get distracted, and often end up out of a room longer than we think...so get in the habbit of turning lights off every time you leave the room.
Check you appliances to see if they're working well. If you have gas, look at the flames while they're running. If they're mostly yellow/orange, it's a good sign that you have poor combustion. Have them fixed or replaced.
SEAL YOUR RIM JOISTS!!!!! There is another thread i posted in that you can find. Rim joists are one of the biggest areas in your house for air infiltration. Get a
spray foam insulation kit and spray your rim joists with at least 1" of foam to get an air tight seal. You'll be amazed at home much it helps!
Seal your duct work! if you have exposed duct work, seal EVERY JOINT with caulk or mastic. You loose a lot of conditioned air through the small seams.
If you have vents, don't just leave them pointing left and right like they come. Many times, you'll find your floor vents point to walls! That's wasted air! You don't want air bouncing around, you want it pointing where you want to feel it. take a pair of needle nose pliers and bend your vent "wings" to point toward your living space. NO VENTS POINTING TOWARDS WALLS ANYMORE!
I'll post more later!