Prevent sun enter through the windows to begin with. This can be accomplished through appropriately sized overhangs, decidious tree for east and west facing windows, exterior shades and curtains, arbors with vines, etc. Another important thing one can do is to paint the exterior of the house a light color, preferably white. This bounces away most of the radiant heat of the sun back into the sky. Even more effective would be to paint the exterior with a white radiant paint such as SuperTherm paint or Insuladd paint. These paints reflect virtually all of the radiant heat from the sun back into the sky. Keeping the house well insulated also helps. Also setting up high thermal mass inside the house with night time flushing of stored heat helps. Planting vines on trellises at the exterior of walls so that the vines block sunlight before it hits the wall surfaces helps. In general, anything that helps to prevent sunlight hitting the house or that helps reflect that sunlight back into the sky is of great help. I suspect that in most areas of North America and Europe, a combination of the tips I just mentioned would eliminate need for any type of AC system.

I like to use a fan rather than the AC. Moving air cools the skin and unlike central air, provides the cooling right where you need it. I find this to be a much more satisfying cool than air conditioning.

This tip is from the day spa, where they keep washcloths on ice for after your emergence from the sauna: Keep a damp washcloth in the fridge. When you're just in from outside on a really hot day, use the coldpack on your forehead and neck to cool off initially.

Glad to see the mention of maintaining clean furnace filters. Another way to green your HVAC system and save a bunch of money is to get a reusable furnace filter. You just pull them out of your furnace and rinse them off about once a quarter and you never produce any waste by using them. Plus, they pay for themselves over time as you aren't buying replacements.

Thanks for practical tips. However, I have my own ways of energy saving tips. It works in summer or in winter. It doesn't use electricity whatsoever, because I manage to build a home under the sun shades. Shade sails gives me more spaces outdoor living room. Electricity usage is quite seldom because it makes me cool and calm because we usually have fun staying outdoors without being out-of-doors.That's why lately people are propelled to adopting this lifestyle. Many are drawing out the use of outdoor living spaces. I use to have this kind of living through my friend in Arizona who manage to contract sunrooms, sun shades structures. I learned a lot of lasting splendor regarding on his expertise and skills on this rising industry. Should you wish to learn and have some info how this structures and designs are becoming a trend aside from its practicality, you can drop by on his site at royalcovers.com. He has a lot lore things to say on this way of living.