There are a few related issues here, which are tightly intertwined:
- How big is my readership? A small readership usually mean comments are few and limited. There's nobody talking, and there's nobody to talk to.
- What's the character of my readership? "Fans of the blog writer", "professional experts in the field", and "buyers looking for product reviews" are three vastly different audiences, even if their numbers are the same. Their commenting and conversation patterns will also be very different - fans will be prone to squeeing and asking the author's opinion on unrelated topics; subject-matter experts will analyse and argue; review-seekers will get their review and never look at the comment section, nor will they have anything to add to it.
- What is my readership's motivation to comment on any particular post? Do they feel like they're helping someone? Setting someone straight? Engaging in a conversation? Making a new friend? If your blog post is nice and maybe informative but doesn't bake in some incentive to respond to it, you can get plenty of readers who just don't comment at all.
As I say, these issues are intertwined. Engagement in the comments can increase your readership; re-focusing on a particular target audience can change the nature and attractiveness of the comment section; bringing in new readers by better marketing can change who's talking in the comments and about what; and so on.
But the point is that these are the three levers you can try to use to get more conversation:
* Enlarge your readership (by investing more in social media; by writing a standout piece that brings eyeballs to the rest of your work; etc.)
* Know your target audience, so you don't stray off-target; modify your target if you're not happy with what you've currently got.
* Be deliberate about what kind of conversation you'd like to see on each individual post, and write the post with that in mind: to encourage the particular conversation you'd like there.
Of these, I'm going to expand a bit on the third point, because it's the one that really involves writing. How do you encourage a particular conversation?
Mostly, you need to be familiar with the different typical types of conversations, and write with that in mind. Types of conversation include:
- Argument: People arguing with your post, or with each other. (Encourage this by taking clear stances, by writing about loaded topics that people care strongly about, and if you're so inclined - by being somewhat inflammatory.)
- Community: Your post is a touchpoint for a community, who congregate around your posts but branch off into all kinds of topics. (Encourage this by being warm and personal in your writing and in particular in the comment section, by treating your blog as a community.)
- Assistance: You provide a question, or a question with a solution. The comments are for the rest of the internet to chime in with their solution, which will help people with the question or problem. (Encourage this by structuring your posts around specific questions, problems, or needs. Explicitly ask readers to chime in with their answers.)
- Conversation: Your blog post provides a theory or a starting point for a wider conversation, where people share their opinions and insights. (Encourage this by writing about clear topics, discussing difficulties and complications, and perhaps avoiding strident, total conclusions. Also, participate in the comments to shape the kind of discussion you'd like to see.)
- Open Floor: Your post is a question you want to put to the readership; the whole point of the post is for people to give interesting answers in the comments. (When doing this, be straight and to the point about this being a request from your readership; otherwise it edges into "Assistance," where you have your own thoughts but readers can share theirs as well.)
I'm sure there are other types I've missed, but this should be enough to give you some types, so you can figure what specific types you'd like to see on your specific posts. Once you've defined that, figuring out how to encourage that specific type of conversation is usually fairly straightforward.
Hope this helps; all the best!