Anatomy is important, attitude is even more. You can make anatomically correct drawings that look stiff like hell because the attitude (movement) isn't there. I like this model sheet of from The Venture Bros because it covers that quickly; Essentially, the way your body moves is mostly affected by your spine, then upper body, and then the lower body carrying everything else.
...so start with the head, then spine, then you can make a rough shape for the pelvis, torso and shoulders. Try to think of the human body as a rigid mechanical thing, it helps with how things assemble and rotate. Usually, you can trace a straight line connecting both shoulders and you'll find the clavicle (roughly). The fun thing is, you'll get varying "V" shapes with the neck in the middle because you can't really lower your shoulders that much. Deltoids (that the muscle on your shoulder) are taller and lower than what most people think. If you keep your arms dangling next to your body, the elbow pit should be somewhere around the end of your ribs, and your wrists somewhere near your balls. If you extend your fingers, you wouldn't be able to reach the top of your kneecaps. Have you seen the classic "I'm a photographer" pose, where girls are sitting in a corner, legs bent and their chin on their knee? That should give you an idea of how long your upper leg actually is. People are usually around 8 and half heads tall (it varies).