I learned this particular tutorial from an artist named Mark Crilley who has a variety of how-to's on his YouTube channel. This is merely the breakdown of one of his videos. Keep in mind that this doesn't teach exactly how to draw each facial feature line by line, merely where exactly they should be placed on the face. Click on the links within the tutorial for a more in-depth explanation of how to draw certain features in different circumstances, via Mark Crilley videos.
1. Draw a circle.
2. From top to bottom, segment the circle into thirds with horizontal lines. The lower horizontal line will represent where the eyebrows should be located. The upper line won't represent anything and can be erased.
3. Draw a vertical line from the top to the bottom of the circle.
4. Extend the vertical line 1/3 of the diameter of the circle and mark with a small horizontal line. This will represent where the line of the lower lip should be located.
5. Segment the extended vertical line below the circle into thirds (1/9 of diameter). The two marks you make here will be where the nostrils, and then the mouth, are located. The actual bottom of the circle does not represent anything.
6. Extend the vertical line another 1/9 of the diameter of the circle. This line will be represent the bottom of the chin.
7. Sketch in the jaw to connect the sides of the circle to the chin line you just made. Note that the jaw line isn't completely curved. There are two fairly straight lines, one coming down from the temple and one bending off towards the chin. More pointy chins = really anime, less pointy chins = more realistic.
8. Draw lines for the neck. Thickness varies between artists, so it's a matter of preference. I like to say that the line for the neck should be half way between the temple and the chin.
9. Draw the eyes typically within the confines of the eyebrow line and the bottom of the circle. For more realistic eye proportions, the space between eyes is typically equal to one eye width.
10. When you draw the hair, you need to first determine where the part shall be: centered or to the right or left? The rest of the hair will fall according to that part. Also, the hair does not lie flat on the skull--give it a little volume and start drawing a space above the top of the skull (the top of the circle). Anime hair is also very geometric a lot of the time, with tons of sharp angles, even in my example above. Keep in mind to add a few as you arch the hair downward.
That's it for facial proportions! You can find loads more helpful tutorials on Mark Crilley's channel, like body proportions for both males and females, faces in profile or 3/4 view, inking, expressions and line-by-line breakdowns. Have fun!