Temp Interior

Appliances: Appliances generate heat, so make sure you have energy star rated appliances. Make Sure your refrigerator door has a good seal. Hybrid Hot Water Heaters actually take heat from the air and use it to heat your water, so its a win win situation. If your hot water heater is warm to the touch, go get some water heater wrap. If you have a window air conditioner, make sure the window is sealed. The plastic adjustable side panels don't work well at all, use aluminum foil and duct tape to make an air and radiant heat seal. You can then cover with a folded pillow case to make it look like a drape. Works and looks great. Check the space between the bottom window and top window, on some older windows, when the bottom window is open to allow for the air conditioner, there is an air space at the top of the bottom window, if there is, seal it. Consider using your microwave and toaster oven instead of your full size oven and range. Saves energy too.

Dryer Vent: Add a baffle or better yet 2 baffles 5 to 6 inches apart in the dryer vent close to where it goes outside. This will help prevent outside air from getting into your laundry room via the vent hose.

Electronics: Turn them off when not in use. They create heat when in standby. Check out these smart powerstrips that turn off other electronics when the main outlet senses the main appliance is off. Electric wall plug timers have been around a while now and are great for lamps and other small electronics you want on a schedule.

Shades: Invest in some good insulated shades to reflect the heat back out the window. A good shade should be thick and have a white outward face. These Roman Shades work well.

Weather Stripping: On Windows and ESPECIALLY DOORS!!
You want to stop air from getting in. You can get this anywhere, even walmart.

Central Air Intake: Make sure you have a clean filter, and replace regularly. Make sure the intake chamber is sealed from the rest of the wall. An unsealed air chamber can pull hot air from the attic down the wall and make the A/C work twice as hard. Make sure there is no furniture on top of the exhaust vents.

Closets: Check your closet ceiling, is it drywall or is it plank? If you find its plank, seal with drywall or aluminum foil and duct tape.

Cabinets: Check your cabinet ceilings, is it drywall or is it plank? If you find its plank, seal with drywall or aluminum foil and duct tape.

Ceiling Fans: Install one in every room that you spent a lot of time in. They make the room feel cooler. You can find them as cheap as $11 when walmart has a sale. Found some for $21 HERE. My Lowes has some for around $25.

Light Fixtures: Insulate the light fixtures so attic heat is not pouring down through it into your living space. If the metal of the light fixture is warm after the light has been off for hours, it needs to be insulated. A $3 can of "Great Stuff" expanding foam can insulate at least 4 fixtures. Insulate the ceiling fan mounting points too.

Computers: Decide on a time when a computer should be turned off and set a scheduled shutdown time. Go into Control Panel -> Scheduled tasks and create a task that runs for example at 10pm and issue the command "shutdown /s" to shutdown the computer to save energy and reduce heat.