Question: How to start writing a book (reflection of past 6 - 12 months)

2014 - 2015 went through a lot of crap (which I mostly created for myself) because of poor choices and a mix of other things, leading to stress and anxiety. I had to go to court (refer to previous forum post of mine), where the outcome was semi-favourable but I lost a LOTS of money in the process. 

So now I want to write a book on how young people, finishing high school, specifically college students can have the right frameworks to make choices that will benefit their wellbeing and their lives. A lot of emphasis is placed on "success" but I realised people need to study failure as much as they study success, and thats the notion I want to place my book on as I believe I have failed, but It has given me leverage to kill it. 

Its a tragedy that so many students especially in the country I live in, how they mindlessly enter college which is 1. expensive and 2. a waste of time if you dont know why and what the fuck you're doing. I will also write about getting active with extra curricular activities and ways to make money as a student, and actions you can take in high school to set you up. 

So I wanted to ask, what is the best way to start writing ?

PS: I have improved, I just got a job for a major electronics company in sales, when I have enough in the bank account as a strong base, I will be moving out again and working on my game. 

Any comments, appreciated.