Here's a simple way to have fun with drawing heads.
Start with a profile. Profiles are easier to draw than intermediate views such as three-quarter views, because you don't have to deal with a lot of depth and overlapping problems. Instead, you can simply concentrate on creating an interesting character. You have fun and choose the proportions, angles, and type of the various elements that make up the head.
Then perhaps you want to see this head in three dimensions. Rather than jump ahead and guess what these other views would look like, you can spend a few minutes building them using this method. That way, you reduce the chance of errors. It only takes a few minutes and a great bonus is that you really get to know your design.
Choosing an angle, you rule parallel lines, as many as you want. Each should run from a key “landmark” such as the hairline, tip of the nose, mouth line, etc.
Then you just draw your views, using those ruled lines to locate the “height” of those facial elements in your new sketch. If you need more information you just go ahead and rule more lines across from the profile, to your sketch. In the example shown, I have chosen to draw two front views, again to keep things simple. One is an upshot on this head, another a down shot. You can also project three-quarter views but it’s a bit more complicated.
In drawing the two extended views, I used a center line placed at a right angle to the parallel ruled lines; this was to keep track of the widths, to make sure both sides of the face were more or less even in width, by measuring with thumb or ruler out from wither side of that center line.
Of course this method doesn’t take into account the effects of perspective; but unless you are very close to the character those effects are minimal. However as I mentioned above, it’s a great way to learn your character, and get yourself in the habit of thinking and drawing three-dimensionally, considering form instead of only line and shape.
It’s often surprising if you first go ahead and draw your version of what you think will be a certain view, and then go ahead and actually construct it according to this method. You can easily be way off. So, you can in this way discover flaws and mannerisms in your approach to drawing heads.
Lastly, this technique can of course be applied to any three-dimensional object you have to draw, so it comes in very handy. It’s also very useful to use this to formally create a three-view (or more) “model sheet” of whatever you’re creating, but I’ll write more on that another time.
Note: the tuft of hair at the top is missing from the upshot...that's simply a mistake.