Myself, when I get an idea (no request/commisions yet) I start with the basic layout of the piece to scale, I then break it up into smaller sections and sketch many different variations, like lefthand forge I like to put them all down, even the wild and wierd this allows me to put togther many different combinations until I settle for one that I like. By drawing to scale I can approximate my material, which for me is gravy on tha' biscuts:). I just recently started doing this and have not yet completed any, so I guess I will see how well this works for me.