In this video we're going to go through how to change the facial expressions based on just the placement of eyebrows. We're going to start off with a circle for a base. 

Let's draw an angry face.

As you already know, angry faces have two straight lines that are bent in words. And let's look at what happens when you move those eyebrows down. I've also accentuated the frown, but you can see it went from a little bit angry to very angry.

Let's draw a worried face.

So, instead of bending the eyebrows inwards and down, we're going to bend them upwards. And if we want to make him look really worried, we can just move the placement on the eyebrows up higher.

For more examples, check out the video.

You want to experiment with placement of eyebrows and mouths. In the video, there are more examples of how you can get lots of variation just through a change of placement.