Technical writing for computer applications imposes special constraints beyond the basic requirements of good prose. Good technical documentation has the following characteristics:
Describe all of the functionality of a product. Do not omit functionality that you regard as irrelevant for the user.
Describe what you see. Do not describe what you want to see. Present your information in the order that users experience the subject matter.
Read http://www.bartleby.com/141/ to help make your writing clear.
Use agreed vocabulary throughout your documentation. Use the same vocabulary as other writers who are working on related documentation.
Review your work frequently as you write your document. Ask yourself which words you can take out. See Section 1.2 ― Golden Rules for a specific guideline.