Separating From Average Narcissistic People

Tip regarding separating from most average Narcissistic people, (other than the stalking or directly abusive):
Simply stop responding, engaging, and giving them positive or negative attention.

You don't need to blatantly ignore them or cold-shoulder them, just stop engaging with them. The point is not to "send them a message", when is the last time you got a message through to a Narcissist?
What will likely happen (except for stalkers/psychopaths) is that they will lose interest in you, because you are not giving them anything.
You're a dry well.
You're a stone in a remote field somewhere.
Narcissists only "like" people and connect with people who give them something they want, even if it's seemingly negative. 

They will now be getting from engaging with you:
No adrenaline rush, no feeling of domination, no challenge, no other supply.
You are now giving them:
No ego-feeding, no caretaking, no catering. no argument, no anxiety reaction, no drama, no praise, no positive or negative feedback.   

When they invite you to a party (so they can leave you out of conversation, say something humiliating to you in front of others, change the date or time, or expect you to clean),
just say you have something else to do that day.
And watch yourself to make sure you don't feel guilt or shame, or anxiety about not going. 
(Remember the old joke about needing to wash one's hair?) 

When they strike up a conversation with you so they can argue with whatever you say, just agree with whatever they say, don't vocalize any of your own opinions or knowledge, and then excuse yourself gracefully. (If you make it look like you're leaving because they're getting on your nerves, that will give them a twinge of supply.)

When they invite you "out" (so they can look "better" than you, or use you as "bait", or leave you out, or leave you behind, or act superior) don't go, have something else (boring) to do, or be tired.

When they change plans and times on you, let them, and then you can't go.

When they are obviously trying to get your praise or attention, give them a polite acknowledgement, but nothing more.

Yes it can feel like arrogance and coldness, but it's not, it's simply not engaging with a person who is trying to provoke you to react and give them something.
If they are not Narcissistic, then you haven't done damage to the relationship, and they will not abandon or discard you (or fly into some kind of tantrum).
If they are Narcissistic, then they'll drift away like there was never any relationship between you, like they barely knew you, and you'll be free from dealing with them.

Most average narcissistic people get bored with people who don't cater to them, or who they can't make react, or who doesn't "challenge" them.
When narcissists are bored with a person, they seek another source of supply.