I have a tendency to chain piece all of my smaller units; progress to the next step with chain piecing, etc. until all the blocks are completed. I use quite a few sticky notes laid out with all my various parts; even with arrows drawn on them so I know which way things are supposed to go together. Still have a few ooops along the way but mostly am able to keep it all straight.
Granted, I sew in a room where I can keep everything out and 'as is' while working on projects and just shut the door. If I was sewing in the middle of the house, say, I probably would go block by block if I was having to put everything away all the time.