Many of us have external battery chargers for our smartphones when the battery life is running low. They are convenient, since they can be recharged and serve as a backup power source when plugging your phone into a wall socket isn't an option. But what do you do with the external charger when it's time to replace it? Most rechargeable batteries can be used up to 1,000 times, but when they no longer hold a charge, be sure to recycle them. The nonprofit Call2Recycle program has thousands of free recycling boxes in stores like Best Buy, Lowe's and the Home Depot, where you simply drop them off. The batteries get stripped and recycled into new products.

Here's another reason to bring your workout outdoors instead of the gym: The treadmill is an energy hog. An average treadmill uses about 600 to 700 watts of energy per hour; that's equal to leaving a few large flat-screen TVs on at the same time. If you spend two or more hours a week walking on a treadmill, the carbon emissions would equal about 1 percent of a car's output. So if it's a nice day, why not go for a walk instead? And whenever possible, unplug the treadmill when not in use, since even in sleep mode, it still uses a small amount of energy.

One of the easiest ways to save water at home is to install low-flow fixtures in the bathroom. Not only is it easy to find low-flow showerheads, you can find even greener options that have a pause button on them. This button shuts off the water while you lather up or add conditioner. When you're ready to rinse off, you just hit the button, and it's ready to go at the right temperature. When shopping for showerheads, look for ones marked WaterSense, which are approved by the Environmental Protection Agency. This mark helps you find the greenest and most efficient choices in stores and online.