In my intro class I spend the first few weeks of the semester going over contour drawing. We draw hands, ourselves, objects in the room, each other with weighted line, cross-contour and blind. It's fun and important but we're all ready to start incorporating value by the end. My second unit introduces value with a variety of mark making techniques. We switch it up and use pen and ink. For some reason students are always thrilled for the first few days of using "old fashioned" pens.
After they've tried out cross-hatching, stippling, using words and other marks they are ready to try to create a unified image incorporating different mark making techniques and a wide range of values. I've changed it up over the years but a favorite is always drawing one's favorite food.
Some examples from this year:
I love seeing the wide range of stuff they come up with, though I do get a lot of images of pizza and burgers! To help them take of pick reference photos for this assignments I show them these images in the beginning to talk about composition.
Of course I encourage them to take their own pictures for reference, but if they don't happen to be eating their favorite food over the course of the project that could be tough so I let them use the internet for reference photos as long as they change things up a bit and don't copy the image they found outright.
This project usually takes about 2 weeks of class time (we meet for 6 days out of a 7 day cycle) for 55 minutes.