Whether you type the text from scratch or work with existing text documents, you must divide the text into discrete chunks of information, or topics. This is perhaps the most difficult aspect to writing online Help: deciding how to divide the body of information into separate topics. To do that you must decide how large to make the topics and where to make the breaks in the content. A general guideline is to keep topics short and present information in small, relatively equal-sized chunks that users can scan easily. However, longer, scrolling topics may be appropriate if the target audience is more expert or if the content suffers from fragmentation when divided into too many chunks.
Exactly how you divide the information will vary depending on the Help project and the specific content. In all cases, you must balance conflicting needs. Small topics provide more flexible ways to organize the information; longer topics simplify the design and help users understand relationships among ideas. In general, try to present one concept or idea per topic and limit each topic to roughly one screen of information. Using this method, most topics should be from one to seven paragraphs.