Make social responsibility an important part of your marketing message. Sixty percent of customers will actually switch retail loyalties if the store is involved in a good cause. Pick a cause relevant to your customers. For instance, a book chain in Texas promotes literacy. Restaurant owners have banded together to fight hunger.
Remember to involve your customers, too. If they donate a used item, you can give them a discount on a new one.
And be prepared to say no. Once the word gets out about your charitable efforts, you'll likely get many requests for help, but it's better to do one project very well than to spread yourself too thin.
Remember, it's a win-win situation. You win, but so does your community.