I do make a plan for each nonfiction book project. There's a lot to keep track of. I have a big spreadsheet that I use with tabs for the entire book writing and publishing process: proposals I submit to publishers; chapter status; schedule; to-do list; reviewers; manuscript submission to the publisher; promotional activities; sales records; etc.

If you want to write to me at karl@karlwiegers.com, I'll be happy to send you one of my spreadsheets so you can see if it would be helpful for your planning and tracking. It's probably overkill, but it helps me know exactly where I am and what I have to do.