I usually start with the head and just estimate with my mind where the body goes on the page. I didn’t jump from nothing to this cos that would be way too hard haha. But I did do the “proper” way of drawing basic shapes first like circle for the skull and maybe oval for the torso etc for years. If you’ve been doing it for quite a long time you will eventually become more confident with your lines and just start looking and estimating the spaces between the head and shoulders and what’s beside them.

If the pose is more complicated then it’s more challenging too but yeah you will gain that intuition once you’ve done it many times. :D