To a certain degree we are all a little self-centered.
But there are others who are a LOT self-centered.
You will always know when you are dealing with a self-centered person, because their actions will always benefit them in some way. Even when they are doing things for others, their motive is how the kindness is making them look, or what they are gaining from doing something nice.
Self-centered people don't think about others' plans. They are consumed with their own.
They tend to cancel previous social obligations because something of other importance (to them) came up.
Self-centered people seemingly brim with self confidence when in actuality a lack of self-esteem is at the heart of their personality. Selfish people do not like for you to disagree with them. Their selfishness likes to be right, even if you present them with facts.
Self-centered people have several superficial friendships, not deep or long lasting ones. They have strong opinions, and will use them. They hide their insecurities and vulnerabilities behind a grandiose persona. They are more than pre-occupied with their self-image and appearance.
Self-centered people can be charming, interesting and fun, at first. But when the attention moves off them, they quickly redirect it back. They view themselves as some special kind of breed, hoping everyone see's their value.
Because self-centered people have no time or energy for others, they tend to only see problems through their own eyes. Whatever hardships you might be having are obscured by their own problems.
When it comes to dating, the self-centered person is more interested in superficial qualities than character. They are more worried about what their friends will think of you, or how you look on their arm. If you don't measure up they will tell you to get in shape, buy better clothes, or get another job. After all, they need you to look good so that they will look good.
Self-centered people are not good listeners. When you take the floor too long, they lose interest and your words become background noise. They interrupt, or talk over you, and they like to have the last word when it comes to making decisions.
Self-centered people usually take charge of things like, decorating the home, plans for dinner, and how we will raise the children. Self-centered people do not like to be undermined nor do they like their image tainted. If you are in a relationship with a self-centered person they will end the relationship if you challenge or undermine them frequently.
Remember self-centered people thrive on attention. When your friendship or relationship gets too hot to handle, let it go. It's not worth the stress to go back and forth with someone who is driven by his ego. Pick your battles, state your case, stand up for yourself, and let it go.
More reading:
https://pairedlife.com/etiquette/Annoying-Behaviors-of-Self-Centered-People
https://pairedlife.com/etiquette/Annoying-Behaviors-of-Self-Centered-People
Difficult Relationships by Luke Gregory