The first step is to search for a decent vertical alignment like the one shown in my line drawing below, after Charles Bargue. It can be useful to incorporate a stationary object into your vertical alignment, like a chair or box. This is because they will serve as reliable reference objects that should not differ in position over the various sittings a life model will make during sessions that can sometimes span over several weeks.
Once at least one series of vertical alignments is found, an imaginary line can be seen through them and represented on the paper with a lightly drawn vertical line (plumb-line).
The topmost point of the figure is lightly marked near the top of the plumb-line, leaving about one-sixth of the paper clear at the top. Also, a point is marked near the bottom of the plumb-line, again leaving about one-sixth of the paper clear at the bottom. This tends to give roughly two-thirds of the paper in which to draw the figure.
The marked plumb-line serves as a known place which relates to the vertical alignments in the observed figure. The next step is to measure how many times the measurement from the top of the head to the top of the shoulders goes into the height of the figure.
In a standing pose this is often between six and eight. Note that generally this won’t be a whole number, so don’t force your drawing or measurements to try and fit one. In fact in my experience, I’ve found that it is common to observe something like 6 + 2/3 heads that go into the total figure height for many adults in the 20 – 40 year old age range.
It is important to measure as accurately as possible as many other measurements are gauged from this. The drawn plumb-line is then divided into the number of head heights. The plumb-line was divided into six in the gesture sketch below.
Plumb-line vertical guide
The vertical plumb-line in the above sketch should be faintly visible. It is now possible to measure the height from the top of the head to the top of the shoulders. Observe how this smaller measurement goes into the plumb-line six times.
This measurement is also used to gauge horizontal measurements from the plumb-line. For example, the left side of the neck to the outermost of the left hand is as wide as two of the vertical head measurements.
The comparisons between vertical and horizontal measurements ensure that the figure in the drawing is not too thin, wide, short, or long. Constantly compare horizontal and vertical observational measurements to these same proportional measurements in the drawing. This will ensure that the drawing stays in proportion to the visual observation as it progresses.
Keep measuring, throughout
A variety of large and small measurements are taken from the figure, and compared both horizontally and vertically. Always take larger measurements, to help retain proportions more accurately. For example, the mid-point of the figure, and marking the corresponding mid-point on (or offset from) the drawn plumb-line.
Eventually, a number of faint crosses are placed. These resemble key landmarks on the figure, which have been measured and checked. These landmarks can frequently be the top and sides of the head; mid-point of the figure; the bottom and sides of the feet; knees, elbows, shoulders and other parts that outline visible forms of the figure.
Gesture and Rhythm
These measured placement crosses are accurate guides used throughout the gesture drawing. The aim of this is to be a concise and simple depiction of the figures’ gesture. Use the pencil as gracefully and lightly as possible, to give you more flexibility when adjusting measurements or line rhythms.
Ghostly C-curves and S-curves should be used alone with a minimal number of small straight lines for the complex parts. Drawn the largest curves first, as they help to govern the overall gesture. Here are some more examples of gesture sketches.
Practice over the top of existing master artworks, as a great gesture exercise. Use a sheet of tracing paper fixed with masking tape over reproductions of master figure drawings and paintings.