Social scientists say that by giving a commitment to something it changes the way that person perceives themselves. This can be utilized in a positive way to encourage people to engage in the desired behavior. Human nature also desires consistency, so once a person commits to something they are more likely to follow through.
It is good to actively involve the person in an activity because then they have a vested interest and will more likely follow through on their commitment. Like the "I voted" sticker, an example of commitment would be to have folks wear a sticker, button or temporary tattoo that says "I compost" or "I recycle."
To influence people to continue practicing a behavior, have them commit to the behavior. Verbal or written, a commitment is a powerful thing.
Agreeing to a small commitment often leads to agreement of a bigger commitment.
Written commitments are more effective than verbal commitments.
Commitment made by a group can also be effective.
Help people see themselves as environmentally friendly in their commitment. They will feel good about what they are doing, and it will help encourage other environmentally friendly behaviors.