Although many research papers that follow the so-called IMRaD format (Introduction, Materials and methods, Results, and Discussion) use these words as their main headings, you can choose appropriate subheadings to help your readers get a quick overview of the scope of your paper and its structure. Typically, readers see the title of a paper and, if that interests them, skim through the paper, looking at tables and figures and headings. And if these look promising, the readers will probably read the abstract. Therefore, headings offer a useful entry point into a paper, and it is important to write them so that they are effective. Here are a few tips.
Draw an organogram: Organograms are typically used to show how an organization is structured and how its parts are arranged in a hierarchy. Since headings serve the same purpose, try drawing an organogram to show the structure of your paper. The main headings will be the first or the top tier; the subheadings will show how a given main heading is divided; and the minor headings will show how each topic that corresponds to a subheading is divided further. Once you have the organogram, use it as an outline while writing the paper.
Limit the number of levels to three: For a typical research paper, three levels of headings are usually enough, although a review paper, a chapter in a book, or a report may have to use more levels. Limiting the levels to three makes it possible for those who skim through the paper to get an idea of the scope of the paper. If there are more levels, the overall picture beings to fade.
Use a consistent grammatical structure for every set of subheadings: Sometimes referred to as “parallel structure,” a consistent grammatical structure means writing all headings under a given heading as nouns or phrases or sentences. In this post, for example, all the subheadings are complete sentences. A paper describing a field experiment in crop sciences, for example, may use the following as subheadings under the main headingMethods: Cultivar, Sowing, Fertilizers, Pest control, and Harvesting. The subheadings under Sowing may include Date of sowing, Depth of sowing, and Spacing.
Do remember that headings are to a paper what signposts are to a route: choose your headings well and your readers will have a smooth ride.
Read this short post to know why commas and full stops should be omitted after headings.