I'd be surprised if you work in the professions and haven't come across a colleague or client that falls into one of these categories. Some helpful insights into dealing with them here.
Emotional vampires are simply immature people who aren't necessarily aware of their own irrational needs. They function based on the fast part of the brain that handles emotions. Subsequently, although you might not change an emotional vampire, you can beat most of them simply by taking the time to think slowly and rationally about their behaviors and the situation.