Before you actually begin writing, prepare an outline. An outline will help you to get a clear picture of the subject matter and allow you to concentrate on one small part of the HOWTO at a time.
Unless your HOWTO is exceptionally small, your outline will probably be multilevel. When developing a multilevel outline, the top level should contain general subject areas, and sub-headings should be more detailed and specific. Look at each level of your outline independently, and make sure it covers all key areas of the subject matter. Sub-headings should cover all key areas of the heading under which they fall.
Each item in your outline should follow the item before it, and lead into the item that comes next. For example, a HOWTO about a particular program shouldn't have a section on configuration before one on installation.
You may choose to use the following outline for a HOWTO about using a specific program:
You may find it helpful to try a little "card sorting" at this stage of the writing process. Write all of your mini subject areas onto pieces of paper. Now sort these pieces of paper into main headings and their sub-sections. It may help to shuffle the slips of paper before you start. This will help to give you a fresh set of eyes while working.
When you are comfortable with your outline, look it over once more, with a critical eye. Have you covered every relevant topic in sufficient detail? Have you not wandered beyond the scope of the document? It is a good idea to show your outline to others to get some feedback.
Remember: It is much easier to reorganize your document at the outline stage than doing this after writing it.