The thing that most people over look concerning high heating/cooling costs is insulation. The majority of housing is under insulated, I was told mine had 32R, when I looked, it had 3R.  Minimal is 32R in the attic (generally, 11 inches). Most people I talk to say they can afford the cost to insulate, but they can afford to pay $200+ in energy bills a month (in case of one member $500 a month), this is crazy thinking to me. Depending on weather, current insulation, etc, one can save 50% +/- on energy bills, so this pays for itself very quickly.  
Shade your house with trees for summer, use deciduous trees (loses leaves in winter) so your house is heated during the winter. I planted Poplar Hybrids, mine grew 6 feet last season.
Use light colors on the outside of your house, this absorbs less heat. Think about that dark roof too.
Attic ventilation, use aluminum turbines. These need less breeze to turn. 
Windows are the worst in temperature exchange. Even high efficiency windows, (double glass with nitrogen fill) are only 3R. I would like to see a manufacture use a vacuum between the glass, a vacuum transfers NO heat. Think of a vacuum thermos, the only reason it looses any heat is though the stopper and when you open it. 
Put awnings above windows to block summer sun but let winter sun in.
Central heating/cooling ducts are only covered in 3R. So all the heat from the attic or under the house is coming right into the house, very inefficient. Most systems have leaks around the registers, so if you close off a room, the heat is blown into the walls. Use window a/c when possible, they only cool the room your in and are more efficient because they don't lose anything though piping.  Use swamp coolers if your region has low enough humidity.
Bathroom exhaust fans, check for proper operation of the check valve. If not proper (or missing) this is a hole leading to the outside.
Of course the obvious, weather stripping.
Use tankless water heaters, heating 30-50 gallons of water 24/7 year around with not in use wastes energy. Tankless also has an endless supply of hot water. 
Personally, my weather is 0-105° and my electric bill for an all electric house has never been over $50 a month, year around. I use a pellet stove in winter which cost me $138 (with tax) for the season last year, aprox $13.32 a month. I'm in the USA.