Doing some painting around the house? It's easier than ever to find eco-friendly latex paint at the store, so look for zero-VOC (volatile organic compounds) brands for your project. Measure the room and use an online paint calculator to know exactly how much paint you need, and don't overbuy. When stocking up on supplies, look for plastic roller trays, cups and paint brushes that use 100 percent post-consumer recycled plastic, which is made from items like soda bottles and milk cartons. Finally, if you want to save leftover paint, try this trick: Cover the can opening with plastic wrap, and tap the lid securely back on top. Store the can upside down (you can place it in a tray if you're worried about leakage). It will be ready to go for next time.