I agree with Vak

CHOOSE SUPERVISOR WISELY

unfortunately, when you start PhD you're not very wise. Nevertheless, signs of an ego maniac supervisor are someone who talks non-stop about how great their research is and how rubbish everyone else's research is! Someone who never listens! Someone who can't not take criticism! Someone who must be in control of everything! Someone with zero publication record in past 5 years! Someone with zero PhD student completions! Someone with zero grants in past 5 years! Don't be a fool and avoid these supervisors or be prepared for the rollercoaster ride. If you do happen to get a ego maniac supervisor, then my advice is massage their ego and agree with everything no matter how crazy. Make sure you get advice on your project from others in the department who have normal sized ego's.