When drawing cartoons its best to exaggerate the attachment of the head, almost as if the head is a toy ball jointed onto the neck. But it can only look this way if the shape design of the head is very solid- the shape cannot look wobbly. In fact, most of the time, the head ISNT volumetrically drawn, when you overconstruct the head you loose the graphic sense of it- most of the time, the outline of the head itself, as a shape, has solid enough qualities to be graphic and solid and the same time, without overconstructing.
And the neck is something you just have to plain get right, because it's part of the spine. If the neck is off the entire body is off.
Especially for the arms, legs, and hands, always refer to other body parts to size it out. Always know your peak, angle, and the width of a limb cross section before executing the outlines. Keep the outer contours of the limbs convex.
Easy cartoon ryhtym (most of the time)- outer contours- convex, inner contours- concave.
If you are going to build a line don't lift your pencil to do it, execute the line as if you're coloring a coloring book. Build your lines for inking things like hair, eyes, and lips, because they have soft complex curves.