Let's be realistic; nobody reads every word in front of them. People skim, but you can use that to your advantage if you organize your writing well and use clear headings to let people find the parts of your writing that they're looking for.

The key to writing good headings is to understand your audience. What key words will they be looking for? What questions will they need answered? Use those words in the heading, state the question clearly in a heading and then answer it in the very next sentence.

In general, it's a good idea to limit the content under each heading to just a few paragraphs. If you're starting a new idea, give it a new heading or a new subheading. Help your reader navigate!