For both woodworking and making downloadable pdf instructions of woodworking projects, I like the idea of planning out all the steps with a physical prototype, usually popscicle sticks, though if there's a group of several different objects or it's a really large scale plan, I think you could use legos for that. popscicle sticks and paper can be great for planning how to build furniture. Various types of software can be used afterwards to make a more accurate model if necessary, but sometimes it isn't necessary. I've really only done the popscicle stick thing once, but it worked, and gave me new ideas and a sligthly better version of my small shelf. When I post about this, I will add pictures of the prototype and a link to the small shelf. I will also add new prototypes if/when i make them this way.