I look at the piece and the end product is in mind as it is just about
to be mounted in the lathe. By the time a spindle project is roughed
out I typically know exactly the shape I'm going to try for.
Mind you I do take some scrap when I go to work out a new design and
practice the new form. I do this with bottle stops. Peppermills I lay
out mentally as soon as the piece is round.

Bowls, totally on the fly.