Be active on website forums your prospective customers are on.
Provide thoughtful responses to questions related to your product or service. Then you can add a link to your website as a source at the end, only if it is appropriate.
Examples of these websites are Quora, LinkedIn, Reddit, Medium.
Another option, if you have a blog (or plan to start one), is to utilize the blogging features on those websites listed above. Just copy-paste some paragraphs from your blog and add a “Read more” link at the end, bringing readers back to your website.
HOWEVER, nobody actually likes to be advertised to! So make sure your goal on those site is to answer their questions first, then if and only if it is appropriate, work your product into the answer.
