I made a short, quick, and dirty explanation about how I approach lay-ins for a different forum. I'll post it here in case someone here will find it useful (or will be able to point to problems with this approach). Here are the pointers: - Use light, thin lines - A good lay-in already has the sense of 3d without any tone - Avoid continuous contours, always look for overlaps - Draw through the form - Think in 3d (study the skull, the Loomis method, whatever else helps) - Make sure the outline has the same feeling as the original (I failed at this step here) - Center lines are your friends - Always check and re-check alignments and basic proportions