Some tips for disposing of old paint include letting it dry out before throwing it away, donating it or finding a safe disposal location for the paint. Some paint lasts up to ten years in the can, so consider whether or not throwing it out is the right decision.
If there is a good amount of leftover paint left, first try to find someone else that can use it, such as a neighbor, friend or relative. Sometimes, nearby schools or organizations can make use of the paint, especially if it is a standard color like white. There are also disposal locations to provide a safe way to get rid of the paint, such as home improvement stores or with charity organizations like Habitat for Humanity. If throwing the paint away, leave off the lid, and let it dry out.