The main proportions for the average human male are kind of like this:

This actually shows the proportions at different ages, but if you were only to do the teen/adult phases the usual proportions of head to body is 6-8 heads on a human body (this is both male and female). To count the 'heads' you measure from the top of the head to the bottom of the chin, and repeat this measurement all the way down the body. For example the adult male in the picture above is 8 heads, while the teen is 7 1/2.
Another tool you can use to make your drawings better is the dummy doll. You don't have to actually use the doll, but the point of it is to use ovals to create what the basic proportions of the body is. This is used most commonly when drawing poses or action shots, because it makes it easier to visualize where each segment of the body will be at a certain pose.
These are just some things you may want to incorporate into your drawings. If you don't already, they're always great starter tools!