Outlines ensure you won't leave out an important part of your storyline. It's a great option that can be used as a brainstorming tool, helping you to develop your thoughts so you know exactly what you want to write. It can help you to formulate your thoughts so you can develop a specific argument with supporting details as you plan out your ideas and structure your project before you start writing.
As you write an outline of your writing project, it can also help you identify the areas of your story that requires more details. Or areas within your project that need to be placed in another area. for example maybe the details in the third paragraph should really be in the first paragraph.
At each stage of my writing process I am constantly asking myself a series of questions to help guide me through the writing process. Will you deviate from your outline? YES!!! However, it will help you stay focused with what you want to write next. Here are more questions I ask myself when I am preparing my outline:
What are the main events within the story?
What is the setting of the story?
Does something move this piece along? If so what?
What problem occurs that needs resolution?
What is the outcome?
Was the conflict resolved? If so, how was the conflict resolved?
Is the story interesting?
Does what you're saying sound realistic?
Keep in mind when writing your book that your descriptions should be painted in such a way that when the reader reads your work they should be able to picture everything taking place as if they were there.