I literally made every mistake a first-time writer could make. I bookended my story--I wrote the beginning, middle, and end. Then, it was time to connect them. Unfortunately, I chose to connect the middle to the end first. This meant that when I connected the beginning to the middle that any story detail that I changed in the beginning--I had to jump forward to make it match the ending parts--this added about a month to the process. I also learned that you had to make your lead character sympathetic and flawed. You want more of the outcast than the prom queen. I also learned that my pivotal moment in my story arc came to late. All these things had to be dealt with.
Then came the never ending process of editing. My first issue was that the average YA book is about 75,000 words. The first draft was 125,000. I edited the manuscript myself the first 2xs. I shortened the text to about 110,000 with the first 2 edits. Then, I talked my friend into editing for me. I thought she would have very little to edit. She was fantabulous and gave me back a bleeding red ink manuscript back. Apparently, writing form 10-Midnight makes me prone to typos and lack of question marks. I had at least 10 full edits before I felt comfortable with handing over the final draft of 96,000 words.