A note on the subject of graph theory...

The comprehension of the material, as well as successful completion of problem sets, is made significantly easier by the use of colored pens. Yes, indeed. Coupled with a competent instructor and a decent text, colored pens (or pencils, if you will, or even markers, if you are a barbarian of that sort) are really essential to anyone's success in the subject. I learned other things too, but this was the most apparent.