Player Types
In the new DMG, there is a section on the different types of players a DM might have in his game. The section goes on to describe what each type of player is looking for in a game and what the DM has to do to make that type of player happy. It also describes what the DM has to avoid with each type of player.
It is a small section, but well written and tremendously useful, especially to a new DM. It is a great improvement on any similar sections the previous editions had in the DMG.