Identify your target, research the target, find the problem, and create a solution. Make a schedule for multi-marketing, and make your online presence through social media, forums, and business pages even if it is personal. Create a professional email with free providers that are not usually used like Proton mail, Create a free website that people don't know about such as Yola, and get a business line by using a local number through a virtual app free. Have a slogan, if you're a business, you will need a logo you can do it with Canva.
Once you have this, now you can start marketing, Post daily on each applicable social media platform in your industry. Create a youtube channel, and do videos on Youtube, Ticktock, Twitter, etc. Join groups, Forums, and engage with potential prospects. Look up business through Google, yelp, etc. Look up key personals through Linekdin, and search them up via Google.
Referrals, Brokers are key to making passive income based on your industry you will have to see what other industry complements your industry. Once you find this out, this is the industry you can find brokers and generate referrals. You can hire commission base workers, to generate your clients where you split the profit. You must be honest and persistent in everything you do.
This is the basics of Marketing. It is no secret, you will find out eventually from experience and research. I just simply put it together and just give you the basics for organic marketing, there is much more to this. You have now the tools, knowledge, and steps to do it. Time, Consistency, Persistent, adapting, and honest doing is the only way this will work out for you.