Many of us use very large capacity water tanks to flush our toilets. One way to quickly and easily save water is to put one or two bricks inside the tank. Saving a half-gallon of water EVERY time you flush will save money in energy used to treat and clean the water, and it will keep the associated CO2 emissions from polluting our atmosphere.
When not using appliances or electronics, unplug them. Keeping them plugged in, even when turned off, still consumes electricity. This is especially true with cell phone chargers.
Plan ahead. Condense your errands so that you aren't running all around town in a disorderly fashion, using more gas than necessary. And if you are at a large shopping center where you need to go to multiple stores, park in the middle so you don't have to move your car for each store you need to go to.
Computers consume much power. Turn off every machine every night if it is not needed. This will save a lot energy.
Keeping your tires inflated to the proper pressure can improve your gas mileage by up to 3.3 percent. It's also safer, and will make your tires last longer (which ultimately results in less waste).
Look for biodegradable doggie poop bags for cleaning up after your pooch. There's a lot to clean up after over the life time of your dog. Help it all return to earth faster by avoiding non-biodegradable plastic baggies.
You know those 50 napkins you usually get with fast food meals? Don't throw them away when you're done. Put them with the rest of your paper napkins and use them for causal meals (probably not when you have guests over). Save some trees, and save yourself some money.
Use blackle.com to search Google and "save a fair bit of energy" as they put it. The darker screen apparently helps save energy. Who knew?!
Follow in the footsteps of blackle.com and make your website's colors darker. This can help save energy. For example: If you've got a centered layout (like TipBin), you could make the sides of the page darker. Every little bit helps!
Make sure to save your cup sleeve from your favorite coffee shop and reuse it. They're usually made from recycled material, but reuse is always far more efficient than recycling. One sleeve should easily last months. There are also plenty of patterns out there that you can use to make your own reusable sleeve.