Prep HVAC System - Make sure you change your filter and check the condenser for debris.
Close Blinds - Closing blinds during the heat of the day will help keep your home cooler.
Use LED Bulbs - They use less electricity and put out less heat.
Buy or Make a Cistern - Having a cistern or a rain barrel to catch water is a good way to save money on your water bill. Water can be used to water your garden or outdoor plants and even clean your car!
Adjust Ceiling Fan - By switching the direction of your ceiling fan, this will cause the cool air to come down and the warmer air to go up! (Of course switch it back when the weather changes!)