Just gonna throw some random thoughts out there.
I coach tennis for a living. Used to play prize money tournaments, been coaching for over 10 years now. Started playing when I was 5. Have gone as far as Spain to do a certification course, but well worth it. I work for myself now, my location allows it. I've worked at 5 star resorts, travelling coach for a top junior player, worked with juniors going pro or college scholarships, adults, etc.
Biggest things I've found is learn to teach everything like 20 different ways. Everyone understands things differently. Some people like a lot of talking, others need to be left alone and given minimal straight to the point instruction. Some people like to shoot the shit during their lessons, others wanna get in a much in that hour as possible. Learn to adapt, learn to talk to people and understand personalities. Not everyone will understand what you are talking about right away, so you gotta dig through and find a way to get to them. Telling someone to do something is ok, showing them is better, but making them feel it gives the greatest results. It makes them understand exactly what you're trying to get across, you build muscle memory and they can repeat it because they know exactly how it should feel like.
Never be late, 5-10min extra if you can works wonders and will most likely give you repeat lessons. Know your shit, and be quick with answers and know what you're talking about. People can smell bullshit a mile away. The best coaches I know are constantly learning, always looking for new and better ways to hone their teaching skills. Look into all types of philosophies, even ones you do not agree with so you can have answers to all types of questions. Develop your twist on teaching methods to stand out a bit. Learn about your strengths and weaknesses as a coach, understand what you're good at and what you need more work on. No one is great at everything.
I've gotten a fair bit of clients on business card alone, always have one handy. I've given my business card away to people who've asked at parties, bars, restaurants etc. Also, don't talk too much about personal things, the client doesn't wanna hear about your shit or your problems.