Typical adult body proportion is eight (8) “heads” (but I think anywhere from 7 to 8 is okay). Below chart notes where each “head” ends in terms of body part:
Another proportion method is 1/3 from top of head to natural waist (just above bellybutton), 1/3 from there to top of knees, and last 1/3 to heel of foot:
The “balls” are joints (shoulder, elbows, wrists, hips, knees, ankles) as well as the stomach as a central “joint” for the torso:
Remember that perspective also impacts your drawing! Eg. The figure here has one foot slightly behind the other so her heels don’t line up to the bottom guideline.
In my unprofessional and untrained opinion, these are not hard rules, just guidelines as you develop your own style and eye for anatomy (but it’s helpful to know what the rules are before you get too cute in “breaking” them).
