"Cigarettes And Chocolate Milk" describes a time in Rufus Wainwright's life when he found himself hungover and pounding chocolate milk to feel better. It didn't work, so he smoked a cigarette, which is when he realized his addictive personality could be a problem.
The Boyz II Men hit "It's So Hard To Say Goodbye To Yesterday" is an a capella cover of a song from 1975 by G.C. Cameron that was used in the movie Cooley High to express the feeling of parting ways with high school friends.
Who writes a song about a name they found in a phone book? That's just one of the everyday things these guys find to sing about. Anything in their field of vision or general scope of knowledge is fair game. If you cross paths with them, so are you.