How to draw a skeleton step by step?

You should start with easy shapes. I use a circle for the head. Then an oval for the ribcage and a shape for the pelvis. Connect them with a line for the spine. For the arms and legs, just use lines and small circles for the joints. This helps you get the pose right. After, you can draw the real bone shapes over this guide. It is very helpful to use a reference picture for the details. This method always works for me.