I enjoyed reading through this section. I never thought of how the signature of your email is self promotion. This is a great tool for if you are interested in networking and might have the connections via email, but not on your linked in network yet.
I think going over the basic professionalism of email communication and in-person drop ins is important for students to remember. First impressions go along way and not being prepared before entering a company or sending the email can pose a problem.