The best marketing is personal contact. Just leaving cards and brochures around public places never got me anything.
I left some cards on aircraft for a while, guaranteeing a free BFR if they didn't learn anything. It worked but not as well as I'd hoped, and now my airport has outlawed the practice, as "soliciting."
I met one student who owned a quick print shop. He made my cards for me. I asked him if he wanted to learn to fly. He said he'd give it a try.
Business owners are much more likely to have the time and the flexible schedule to learn to fly.
I met one guy while stopping to help at an accident. He was the EMT. He is now working on his commercial.
Two students were linemen. They both went on to be pilots at airlines.
The vast majority of my students were referrals, however. Referred by people who had flown with me, people in my club, people who worked at the airport.
They "knew" that I was the "go to guy, who was hanging around the airport wanting to fly." They also knew that I was "a good instructor, who enjoyed instructing."
The FBO is where the action is. If you can get a job there, either full or part time, you have a definite foot in the door.