Effective observational writing employs many different techniques, yet must always do so with purpose. It is not useful to describe everything about a subject. If this occurs, a reader will become bogged down with inconsequential information. Rather, a writer should be careful to focus his or her attentions upon a clear dominant idea. Ultimately, successful writers are able to focus primarily upon details and images which enhance or expand upon the reader's understanding the dominant idea. Knowing what to exclude from a piece of writing is as important as knowing what to include.