There is no real "right" way to approach writing a story. An outline, be it a bulleted list or a mind map, is something that can help provide a guideline for your story and your chapter breakdown. These can take on a variety of formats, including:
More of a mind mapvs. a formal outline
I bet most of us are taken back to something done in English class growing up, and perhaps a few feel outlines are too constricting, but having an outline is there to help you. An outline is what keeps you from ending up confusing the length of your chapters with actual passage of time, from pouring too much plot into a single chapter, and from feeling "stuck" before you are ready to end your story. At the same time, one doesn't want to over-plot the story and feel stuck to something when perhaps more creativity strikes around chapter 15.
Over-plotting: when you find yourself forcing your characters to go through certain pre-determined motions that may not fit into how their personalities have developed, simply because you are trying to fit into your already-established, overly-planned plotline.
Outlining but not Over-Outlining: Tips to Strike the Balance
1. Write your synopsis first, so that you have a clear idea where the story will end before you even begin. This helps you get an idea of where each character's development will need to be by the end and what will need to happen before the end so that the reader is able to take away certain points about the character (e.g. what struggle are they going to have to overcome/deal with to get to the end point? What will that character or relationship be like in the ending?
Basics of a synopsis: Major plot points (no detail need be included), characters, and a basic outline that conveys the gist of what will happen without going into details that might inhibit later sparks of creativity.
2. Insert Chapters into your outline - a few sentences at most - that'll just help you establish and maintain a focus for each chapter. This will help you know the point of a chapter so that writing the next feels more natural. This will also help you set your pace. This way you won't end up with everything happening super quickly or having things move too slowly. Oh, and for this to work, stick to it. Don't let a chapter end until it's completed it's purpose.
For the more ambitious authors:
3. Outline your main characters. Develop their personalities beyond the unidimensional norm. Look back at the beginning of your outline and the conclusion, think about how their personalities/way of being might change during that time. Then look back at the events you have outlined and think about how each will contribute to the development of that character. Perhaps add in the outline "X is upset" or "x begins questioning her sanity". Something to give you a guide on how your character(s) will react to the event.
Caveat: Refrain from adding more conflicts for your main character/OG to overcome. Adding too much stuff/drama just weakens the plot and makes an eventual pairing with Michael (as is the most frequent premise), more unlikely.