Podcast interviews
Because I wasn't pushy nor spammy, most people were more than happy sharing my content on social networks (some even linked to it).
It is easy to compile a list if customers, business partners and other reliable websites that allows you to leave a testimonial. You can also include a link directly to your website in that testimonial. Google reviews are a great place where to start. Referral links are also a good place to start. Particularly important if your company is just starting out.
You can subscribe to HARO ("Help A Reporter Out") to get started. This is an unpaid service that connects journalists and experts looking for contributors with expert sources, such as yourself.
There are times when you can include a link in your comment. However, most of the time, the comment must be written for the sole purpose of building a friendship with the author.