Design is a tricky thing. Changing one thing can alter the aesthetics of a piece considerably. When I draw, I don’t use dimensions aside from the component sizes. I prefer to place a fixed shelf where it looks best, not where some mathematical formula tells me to put it, like the golden rule for a perfect rectangle. I might move a shelf ten different times before I’m happy with its placement. This happens because I need to work within the confines of the component sizes. I can’t have four different thicknesses of shelves.
Back when I used to hand draw with a scale ruler and graph paper, I used a lot of white out, a whole lot. Now-a-days I draw rough sketches and then AutoCAD the drawing. I end up making a lot of changes as I work through the design with the customer.
I designed a couch for a customer several years ago. We liked the way it turned out, and made it a standard piece. The original drawings are below, with a variety of chicken scratch notes made on the sheet. There is a whole write up on how to build the piece in addition to these notes, but it all starts with the design.