In order to draw proportionate bodies, the height of the person should be about 7 times the "height" of the head, like illustrated on the  drawing on the left.  

Notice that, for a  woman, the nipples are about spot on the line of the second head lenght.  (wow, what a sentence O_O;; ) what I mean is that the nipples are on the 3rd line from the top!  There! You still with me?  good XD  

I don't really have any other reference points for the body in general though (besides the head lenghts and the breasts): I just try to make the proportions of the legs and abdomen look good.  

Notice that for a man, the BOTTOM part of the breasts is on the 3rd line from the top, not the nipples.  

Note that for children, a complete other reference system is used: the 7 heads lenght is NOT used, since the children's particularity is to have a big head compared to their body.  

Useless (Yet Interesting) Facts

In ancient Greece, a similar system was used in sculpture.  Normal human beings were 7½ head-lenght high,  while heroes were 8 head-lenght high and Gods were 8½ head-lenght high.  

I got this information from a magazine: 

PARRAMON, J.M., Peindre & dessiner, "Le corps humain", Hebdomadaire N°7, Bordas, Larousse.  

Arms

Another good thing to notice is that the elbows are lined with the waist, and the hands are lined with the crotch.