It's impossible to overemphasize the importance of narcissists' lack of empathy. It colors everything about them.

I have observed closely some narcissists, their inability to pay attention when someone else is talking is so striking that it has often seemed to me that they have neurological problems that affect their cognitive functioning.

They borrow their opinions and preferences and tastes from whomever strikes them as authoritative at the moment. They fill in their lives with bits of behavior, ideas, tastes, opinions, etc., borrowed from someone else whom they regard as an authority.

They are evidently transfixed by a static fantasy image of themselves, and this produces an odd kind of stillness and passivity.

Narcissists don't talk about their inner life -- memories, dreams, reflections -- much at all.

They seem not to make typical memory associations -- i.e., in the way one thing leads to another, "That reminds me of something that happened when I was...of something I read...of something somebody said...."

They don't share their thoughts or feelings or dreams. They don't say, "I have an idea and need some help," or "There's something I've always wanted to do...did you ever want to do that?"

They don't tell how they learned something about themselves or the world. 

Narcissists are threatened and enraged by trivial disagreements, mistakes, and misunderstandings, plus they have evil mouths and will say anything.

Adult narcissists are like vampires: they will take all you can give while giving nothing back, then curse you for running dry and discard you as a waste of their precious time.

Remember that narcissism is a personality disorder and narcissists' personalities are disordered: they don't make sense! They are not concerned with making sense and they are also impulsive, so you will waste your time trying to understand the details of every little thing they do.