Look closely at who your customers are. Find a cause that touches local concerns or a prominent challenge in a target industry. I admire those folks for doing something about an issue I care for. Include a mention of your charitable activities in all your company correspondence and marketing. Most large charities are highly adept at getting media coverage.
Media outlets know it is good business to join with non-profits as partners.
Media supplies publicity as their contribution. Because the audience appreciates and expects media to participate in community improvement efforts, programmers and editors make sure their non-profit activities get good coverage. Offer to contribute time, goods, services, or cash. Ask if your company logo can be included in ads. Your name can be mentioned in radio public service announcements and talk show interviews.