Octavio Rodriguez: Making faces out of shapes....

Here is one of my methods to quickly knockout some shapes for faces. 

First I'll start to draw a bunch abnormal circles, as below:

Then use those shapes as the foundation:

To make these rough sketches:

Here's another example, just a little more dissected:)

Draw some shapes:

Draw the accents for the face (nose, hair, ears, etc...)

Ending up with this final result:

This process I find helps to keep you loose and also keeps it fun as you discover shapes you wouldn't normally create.  Because your focus is on the specific details from the beginning then looking at the overall design:)