An effective user manual is, first and foremost, one that gets read. Secondly, it is a manual that actually helps its readers. rtfm* shows you how to figure out what to write about, how to organize the material you've selected, and how to write it (including the grammar rules you learned in school that you should ignore). You'll even learn the basic rules on how to lay out your pages to support readers looking for information. And, like any good user manual, it's only as long as it needs to be.