Turning photo or multiple tone image into a cartoon

Hey, I have this design class and I have to change a portrait into a 2 toned image, then a 3 toned, then a 4 toned. anyone have an advice on how to go about this? here' the image i want to use: http://www.digitalmatt.net/mainpic1.jpg

I would start with the cutout effect (effect/artistic/cutout). Play around with those settings to see if you get what you want.

Some tutorials to try for ideas:
http://www.photoshoplab.com/tutorial_Easy-Two-Tone-Silhouette.html
http://www.graphicvisuals.com/tutorialvectorart.htm

use posterize in image menu > adjustment > posterize