In my 2D class, aka "tooty class", we did an object exploration drawing three different objects using only pen and ink. Pen and ink meaning a bottle of ink and pen nibs which I had never used before. These were to be line drawings - only lines, hatching, and cross-hatching.
After we explored our objects, we chose one to expound on. I chose a toy airplane. Then we did five concept drawings of our object (pictured here). In class we had a silent critique, where we walked around to other's sketch books, looked over their concepts, and wrote down our favorite and least favorite stating why. Then from that feedback we chose one concept to redraw on a cold press board for the final project to turn in.