Check your toilet for leaks. Put dye tablets or food coloring into the tank. If color appears in the bowl without flushing, there is a leak.
Amt saved: 400 gallons a month.

Keep a bottle of drinking water in the refrigerator. This beats the wasteful habit of running tap water to cool it for drinking.
Amt saved: 200 to 300 gallons a month.

Instead of incandescent lighting that use a lot of energy and burn out quickly look at fluorescent or LED lighting instead.

Fluorescent light bulbs use 70% less electricity, give 5 times more light, emit 90% less heat & last 10 times longer than regular bulbs. You can also choose LED lights that use at least 75% less energy and last up to 25 time longer.
Amt saved: $50-75 in electricity costs over life of bulb.

A home with inadequate attic insulation can lose as much as 40% of its cool air. Because heat rises, as much as 60% of heat can be lost in the wintertime in poorly insulated homes.

When washing dishes by hand, fill up the sink with soap and water instead of running the water the whole time.
Amt saved: 25 gallons per load

Thaw frozen foods in the refrigerator, not under running tap water.
Amt saved: 5 or more gallons per meal

Replace furnace filters every month. Dirty filters make your system work harder & run longer than necessary & encourages buildup of mold & mildew, which can make cleaning more difficult.

Dry loads of clothes back to back to take advantage of heat built up in the dryer. Clean the lint filter after every load. Your dryer will dry more efficiently, requiring less running time.