Try to buy only the amount of paint you need so there is little to dispose of when you complete your project. If you do have leftovers, follow these guidelines:
Save small amounts of leftover paint for future touch-ups. To keep it fresh, place a layer of plastic wrap over the mouth of the can before replacing the lid. Pound down the lid securely.
Check with your local waste collector to see if it accepts dried latex paint. If so, place the open can in an airy spot away from children and pets. When the paint is completely dry, put it in the trash.
Seal oil/alkyd paints in the can and store them safely away from heat sources until you can take them to an appropriate waste-disposal site, such as community paint/stain collection events where you can safely dispose of leftover paints.
Never pour paint, stain, or any other coating down a drain, into a storm sewer or anywhere else that might contaminate the environment.
