An outline is useful for a number of reasons, principally because they aid the writing process, organizes material logically and crystallizes an orderly overview of one’s writing.

To create an outline, it is first necessary to realize the paper’s purpose, its audiences, and construct a thesis.

The following are four suggestions to be used for a well-written outline.  

1. Headings and subheadings should contain a consistent style.  For example, if the first heading is a noun, then the second too should be a noun.  This is known as parallelism.
2. Another guideline is what is known as coordination.  In other words, information contained within each heading should reflect a consistent significance, and this goes for subheadings too. 
3. Headings should also be more general in specifics, whereas subheadings need to be more specific.  This is called subordination. 
4. Each heading needs to be divided into 2 or possibly more parts.  There should never be just one section under a heading.  This is called division.