Here is one example of a design process that I use occasionally. Neil Helm had a very specific character designed in the written sense. We just needed to translate that into the visual sense. Based off of the information he gave me, I felt that a good starting point was the character's face. The reason being, is that I perceived face to be the primary means of emoting for this particular character. If the body is the window to the character's personality, maybe you should start there.