Heading Tags have become an important part of a well-optimized blog post. I have seen people always wondering the correct number of heading tags (H1,H2,H3) which they should use in their article. While there are no strict guidelines which you should follow, here is a structure which I always follow as it actually works for me:
Your Post Title - H1 By Default
Sub Heading in your Article (H2)
Another Sub Heading or a Major Point (H2)
3rd Sub-Heading (H2)
Less Important Note/Heading (H3)
There isn't any limit for using H2 and H3 tags but I always prefer to go with 3 H2 Tags and 3 H4 Tags. I'd never suggest anyone to use H1 tag anywhere else apart from the Post Title which is already H1 by theme default.
If you're using Yoast plugin for WordPress, you would notice that it always suggests using focus keyword in H2 tag. Hence, I always go use focus keyword both in H1 and H2 Tag. Although it's not a necessary but it's still worthy.
Let me know your opinion and the heading structure you follow for your blog posts.