Having curtains drawn is a great way to keep the sun from coming in to heat up your house and to keep the air conditioned air inside the home. So, curtains are key.
Summer nights can be cool. So, I keep my windows open at night and immediately upon wakening in the morning, I close them and draw the drapes.
Air circulation in your own home can keep a house cooler. I figured out that if I open certain windows in my home, both on the first and second floors, that it creates a great cross breeze. So, play around with your windows to see if that can help on days that are not horribly humid.
Fans are great for circulating air as well and can be used at the same time as the air conditioning to increase it's effectiveness.
A dehumidifier is fantastic to take water out of the air, which decreases the ambient temperature.
Wearing cotton clothing and avoiding ALL synthetic fabrics and synthetic blends (POLYESTER) will keep your body cooler as cotton, linen and even silk fabrics allow your skin to breathe. Synthetic fibers retain your body heat and make you feel hotter and reduce the ability for your body sweat to evaporate. Sweat evaporation is the body's natural way to cool down, so don't wear synthetic or synthetic blends.