@KearaSeeley Typically I stick to the plot of the book and add side plots (like a fight or an interesting twist) I make a paragraph or two at the end of each chapter (and delete it before publishing) so I know what to achieve from the particular book. To keep interest I would say to write everyday, but you dont have time lol, so as to that, I would probably tell you, write something close to your heart. Like when I was writing The Gang Leader And The Fighter I felt (at the time) that Sasha was like my alter ego or someone I wanted to be like (attitude wise because she had some sass). Make the characters/plot like something or someone in your life so you always find yourself going back to that book. For the time part: while writing The Gang Leader And The Fighter I used to write for about two hours while my parents thought I was asleep at night. Because I couldn't write in the day (because I kept this account away from their knowledge) so I only had after hours in my bedroom between 9:30-12. Most nights were exhausting and I only wrote maybe a paragraph. What I'm saying is you make time for the book when you feel committed and comfortable, I felt successful while writing the book and I had confidence. When you feel confident in the book you find yourself writing in it everyday, whether you had time for it or not..
I really hope my advice helped you, thanks for coming to my profile to ask me about it :)
-NC