I always start with an outline! I use different methods for measuring the distance between facial features. I NEVER just guess the distance! It became obvious to me early on in portrait drawing, that there are precise measurements involved? It's a crucial part of making a person look like who they are! You can use rulers, markings on scrap paper, grid paper, etc. The outline is not a fast sketch either. If you don't get it right, the whole drawing is off!