I write a lot online about machine learning (especially for a broad audience). I don't do it intentionally as a marketing strategy, but people researching those

I write a lot online about machine learning (especially for a broad audience). I don't do it intentionally as a marketing strategy, but people researching those topics naturally read what I write and some email to ask if I can help them with their projects. That leads to connections and sometimes to new projects. That's the best way to market other than just meeting people and networking. The real skill you have to develop is who to say "no" to. One good customer can keep you busy for a year and pay really well. 500 bad customers with small projects and small budgets can require 500x the work and result in less overall money. I got my first customer that way and most of my best customers that way. But once you get a couple of customers and do a good job, that naturally leads to more work and other opportunities through word of mouth. Another strategy that has worked for friends is to contract part-time for a place they used to work that needs temporary help. One friend made nearly his full-time salary working half-time doing this. That left him with the other half of his time to work on his other projects. One other strategy that works well in a big city is to go work in a shared office like a WeWork. It's easy to meet people that way just through proximity and end up doing projects together or get new leads.