You can't do sketches enough. Sketch everything and keep your curiosity fresh.

John Singer Sargent

Portrait Drawing Lessons | Proportion

Within my initial arabesque (contour) the proportions are set and the facial arena economically mapped.

The oft taught practice of placing the eyes in the vertical center of the head has set countless artists down the garden path to a dead-end. It is only when looking at a sitter straight-on are the eyes centered vertically. And not always. Once the head tilts forward or back the proportions change significantly.

It is many times preferable to first establish the brow line: the measure of the supra orbital eminence (the browline) to the mental protuberance (the chin) possesses a geometric specificity that reciprocates throughout the entire head. It is the primary measure for establising facial proportion.