As to what to include I write my log for myself. It includes everything I want to go back to the next year to refresh my memory for the new grow. It's also helpful to have the timeline so you can expect the issues you had the previous year to apply the fix proactively
I made a journal type deal using accounting paper this morning. It has places for the date, comments, and a numbers column on the right so I can track expenses. I can keep receipts in the back. I'll transfer the highlights here when there are some.