A few years back, I had the horrible experience of working for a narcissist. Unfortunately, there are plenty of narcissists in management, so if you don't end up working for one, you'll end up with one for a customer, sooner or later.
In my case, while he'd charmed me during the job interview, I realized something was "off" when a co-worker described how he drove to work each day: at 100 MPH (radar detector) while drinking coffee and smoking.
That he was putting everyone else on the road at risk of dying meant absolutely nothing to him. And it was all downhill from there.
Anyway, in the five years that I worked for this world-class jackass, I learned--the hard way--how to get things done despite him and around him. Here are the rules:
1. Don't take his promises seriously.
Narcissists are selfishness on steroids. While even selfish people feel some sympathy, narcissists only care about themselves.
To a narcissist, other people aren't real. They're only pawns that need to be moved around to get narcissist what he wants.
If he needs you do something for him, a narcissist will tell you what you want to hear. Whatever he says, however, can't be taken seriously.
The moment it becomes inconvenient for him to fulfill a promise, it's as if the promise never existed. It's not real because, to him, you aren't real either.
2. Never tell him that he's wrong.
A narcissist can't tolerate losing because losing threatens the grandiose self-image that he's trying to project.
A narcissist will treat anybody who gets in his way as an enemy who must be not just defeated but belittled as well.
When a narcissist does lose, he will claim that he "actually won because..." When confronted with evidence he's been bested, he'll claim the other person cheated.
If presented with evidence that he lost "fair and square", a narcissist will deny that he ever competed.
3. Don't fall for his charm.
A narcissist can turn on the charm when it's in his interest to do so, like when soothing the emotions of those he's cheated or lied to.
Narcissists love to appear magnanimous. For instance, he'll publicly support a charity but wriggle out of paying when he thinks nobody is looking.
An easy way to spot a narcissist at work, BTW, is to surreptitiously examine the payment folder at a restaurant after he's ostentatiously "picked up the check."
If he thinks he can get away with it (for instance, if he's on a business trip), a narcissist will stiff the waiter and not leave a tip. Every time.
4. Work through his enablers.
A narcissist who obtains a position of power will surround himself with toadies (often family) who become expert at manipulating him through his vanity.
Unless you're planning to become a toady yourself, you'll need to work through the toadies to get the narcissist to fulfill any commitments.
For example, if you ask a narcissist for a raise and he says "yes," you have no idea whether you'll get the raise or not. (See item 1 above).
However, if you get the narcissist's toady to work the issue for you (perhaps in return for a favor), the toady may be able to maneuver your raise onto the budget.
5. Be glad you're not him.
Look inside the soul of a narcissist and you'll find an emotional black hole that sucks up everything but can never be filled.
There's no amount of praise, no amount of possessions and no amount of fame that can ever make them feel whole.
Because other people aren't "real" to him, a narcissist has no friends. He can't have sex--not really--because he can't make a connection.
Everyone, including family and sex partners, are cardboard cutouts in the shadow play of his life. Whatever his accomplishments, a narcissist lives and dies alone.