You spent time writing an article. Your visitor may have a minute. They often start by looking for an answer to a specific question. A wall of text makes that harder than it needs to be.
In the original 2011 version of this article, I argued mainly that headings were good for search engines. That was too simplistic. The better reason is that headings reveal the shape of your argument. Readers can choose the relevant section, and you can see when your own writing wanders.
Start with the reader's questions
Write down what someone needs to know. On a page about order delivery, “When will my order arrive?”, “How can I track it?” and “What if it does not arrive?” would be useful headings. “Other information” says almost nothing.
A heading does not need to be clever. It needs to describe the section honestly. If someone scrolls to “What does it cost?”, they expect a price or a clear explanation, not the history of your company.
Give each section one job
A heading only helps if the paragraphs below it belong together. If one section jumps from delivery times to warranties and then payment methods, split it. If a section has a single sentence that adds nothing, perhaps it belongs in the previous paragraph.
There is no fixed word count at which you need a new heading. Add one where the subject changes. Put the main answer early in the section and details afterward. Short paragraphs and lists can help too, but ten unrelated thoughts in bullets are still a long, unfocused text.
Make headings reflect the structure
A web page usually has a main heading for its title. The main sections of an article can then use h2 headings, with h3 headings for sections within them. Choose a level for its place in the structure, not for the size of the type. The W3C's accessibility guidance explains how a clear sequence also helps people navigate with assistive technology.
Search engines may use headings to understand a page, but an h2 does not promise a higher ranking. There is no reason to force a keyword into every heading. Tell visitors what they will find there.
Read only the headings
When you finish, read the title and headings on their own. Can you follow the argument? Do two headings promise the same thing? Have you missed the question that likely brought the visitor here? Fix the structure before polishing individual sentences.
If possible, show someone else only the headings and ask where they would look for a particular answer. If they choose the wrong section, you have useful feedback. Good writing does not have to be short. It should let readers reach the right part without a search. That applies to a customer story as much as a help article.