Getting started -- Talk with another, non-competing, business owner. Set up an open house at your place or at the other business. Both businesses invite current customers/clients with phone calls, emails, Facebook announcements, Twitter tweets, maybe even a news release. Get the word out to as many people as you can.
Facebook is the busiest destination for small businesses to get the word out in the world of the Internet--and passed around. There are others. Many businesses get good results using Twitter, Instagram, LinkedIn, Pinterest, and others.