Teaching.

Set up some sort of online, or even better, night course at a local college.

Charge for it.

By teaching, you set yourself up as an authority on the subject. The more you teach, the more people see you as the person who knows those most on the subject.

What you'll get out of it is more business referrals and more clients.

Seems weird, and most people will say "you'll be training your competition!" but in fact, you won't.

Just because you teach someone how to use a camera, it doesn't turn them into a professional photographer, but it does form a relationship of trust and knowledge between you and boatloads of potential clients.