How should I format blog posts ?
Formatting your blog posts can be done in any number of different ways and it's really preferential depending on who you are and your writing style.
For the most part here on this blog, I tend to start out with H1 tags in the title, for any subheadings that I may use, I'll use H2 or H3 and then no heading typically for the remainder of the body text and content.
I will bold information when necessary if it's a point that I want to illustrate with greater meaning beyond what I've added to the general context of the blog post and I'll use 2 to 3 images per 1000 words in each blog post for my longer blog posts.
Aside from that I have changed from writing in 4-5 sentence paragraphs to shorter paragraphs (3-4 sentences) as they are easier to read, particularly if I'm writing a long form post.