Start with a simple ribcage and torso shape
Mark the chest area and shoulder line
Sketch the breasts as soft, rounded forms attached to the chest
Keep the shapes natural and varied in size, position, and angle
Indicate gravity by letting the forms rest and hang from the chest
Add the undercurve and side contour lightly
Refine the silhouette so it connects smoothly to the torso
Add the nipples and areolae if needed for the style
Use light shading to show volume and form
Adjust symmetry only as much as the pose requires
Erase construction lines and clean up the final drawing