If you think of the borders of the reference photo, consider that it is a square, i.e. equal sides. Try using that square in your drawing. First, draw the square box as an "envelope" for the figure. Now, draw the shapes that are "not figure". You can carve away the spaces and be left with the figure. Drawing the negative spaces as shapes will increase your awareness of the relativity of the positive shapes. Proportionality is all in the angles. Big to small... General to specific. Keep your lines light, loose and explorative... 80 percent looking... 20 percent drawing. I hope that's useful.