I am sure you will get a number of good ideas. I am not sure there is one ‘best’ idea, because location, size, competition, available mass transit, type of offerings, focus, etc…. there are so many variables.
One general thing I would say is that with the people I have seen succeed there are some common things. First they understand social media and have update their online presence and respond to people who reach out to them on multiple platforms. This is less vital for a one person show, but was the case for some places i have watched do well, and not so well lately.
Also, getting to know other local businesses is very helpful. I know of a case where the local coffee house chose to send people to one place over another. I was not privy to the reason why they took that action…. but a ton of traffic went through that place. You might have lots of friends through the city talking about you, and that is great…. you might know a lot of people in your industry, and that is great also…. forging good connections with local physical therapists or massage therapists and so on is great…. but if the owner of the hair salon down the street talks to everyone in her chair about the killer ab class she had that morning, or the local coffee house puts up your schedule and tells people she works with you…. that is really golden.