Keep blinds and drapes closed during the day: Radiant heat from the sun makes a huge temperature difference. Go to any home in Europe in the summer months and the shades are always drawn during the day for this exact reason.
If you install an A/C window unit make sure it’s on the shady side of the house and in a window towards the center of the room you're cooling: If the unit is in a cooler area it doesn’t have to expend as much energy to run, and if it’s placed in the center of the room it will distribute cool air more effectively.
When you aren’t home, don’t run the air at full blast: It’s wasted money.
Landscape for coolness: Trees offer a tremendous amount of shade for homes when planted to block particularly sunny spots. This is a long-term fix …
Avoid using the oven and the dryer: Don’t make the house hotter than it needs to be.
If your A/C unit is more than 10 years old it’s not energy efficient: It’s expensive to buy a new unit, but you will see a distinct improvement on your electric bills with an energy efficient model.
Use fans: Even if you are running your air conditioner, run the fans as well. You can set your thermostat 4 degrees warmer with fans running because of the increased airflow.