Honestly, its easy to identify an energy vampire just by their behaviour: they are usually the clingy type, paranoid, not happy unless an intrigue/conflict exists and a gossip monger.
I have to deal a few people with this type of attitude and for awhile, I thought that there is something wrong with me. The only thing that was wrong with me was making the mistake of associating myself and making a lot of efforts to maintain that relationship even at a personal cost of being uncomfortable, tired, upset and stressed.