Look for these characteristics: 

• They create a false persona as a protective barrier – like a false identity. 
• They can be very likable - at least at first but the closer you get to them, the more their true character traits come out.
• They lie, are evasive, give half-truths and flat-out contradict themselves.
• They gossip, smear and slander because the goal is to turn others against you in hope that others won't try and figure them out.
• Lack of empathy.   
• They have very little interest in introspection.
• They control with playing manipulative hot and cold games.
• They have an underlying sense of entitlement and grandiosity.
• Some like playing the victim role to get attention or to twist the issue so they don't have to look inward to make changes in themselves.
• Exaggerated sense of "self-importance".
• Expect to be recognized as important to others without achievements that warrant it.  Especially in their marriage relationship.
• They are unable to have deep heathy and happy relationships because they will not connect emotionally.
• Constant denial of damages they inflicted – if they do admit, it's at a very minimal emotional level.  Narcissists tend to externalize blame, pinning the blame on everyone but themselves.
• Have the inability or unwillingness to recognize the needs and feelings of others.
• They are destructive and self-defeating in their marriages.
• Failure to recognize others emotions, feelings and needs – especially closer relationships.  
• Fragile self-esteem but appearing tough-minded or unemotional – except for anger.
• They don't feel guilty or convicted for hurting others, they will just continue as normal as though nothing has happened or blame-shift..
• They have difficulty regulating their own emotions and behavior which exacerbates the problems they cause.
• They are known to use things to anesthetize themselves to escape the "emotional realm": drugs, alcohol, affairs, gambling, internet, sports, television, video games, pornography, etc.
• They will control you with withholding affection.
• Extra marital affairs are prevalent because it boosts their self-image and is noncommittal; even if they have a loving spouse.  
• Pornography fills a fantasy relationship that they can control in their mind and there is no risk; which also can give them a fixation with masturbation because it gives them physically what they need without the burden of “emotional connection”. ​
• They shun the ones who truly care and are trying to help them because they do not want to look and see that they have something wrong with themselves. 
• They "perceive"truth being told to them as insults.
• They can be very unforgiving and usually are revenge seeking.
• Narcissists may show passion in the early stages of the relationship (love-bombing) but that soon dissipates once they feel they have your heart. At that point, they demote you. (another form of control)
• Many times, they monopolize conversations so they are the center of attention.
• They experience major problems adapting to change because they want to control.
• People are things to be used for their benefit to fill the lack of emotional needs that weren’t met as a child.
• They eventually sabotage or destroy their good/close relationships especially in marriage.
• They often isolate themselves especially if they are being exposed.
• They show patterns of manipulative, controlling behavior that involves both emotional abuse and emotional manipulation.
• ​They usually have underlying depression and anxiety from neglect and/or abuse in childhood. 
• They keep their surface relationships, so they won’t be lonely (again, another form of using).  
• Personal relationships are usually at a surface level because this would require them to be vulnerable and that is “perceived danger”.  
• Narcissists generalize that all are harmful and cannot be trusted.  
• They are very defensive and self-protective.
• They will sidestep your questions doing things to make you suddenly forget what you were asking. Narcissists can be very skilled at dodging and ducking questions they don’t want to answer. If you press them, they will then “slot” you as “unsafe” and will begin to avoid you.  
• They often display condescending or patronizing attitudes.
• They will appear to be your friend and keep you close to themselves (so it appears) as long as you are useful.
• They can be giving but it will  always be from a non-emotional level (material items).
• ​Men are more likely to be narcissistic than women. 
• They are all about control to the extent they will push the people who genuinely care about them away so they can "feel" a level of control.  This disfunction derives from painful things happening in their childhood that they had no control over.

 
Christian perspective:
Jesus can heal.  This person must go back to childhood wounds and face them but also know that Jesus will help them change if they allow Him to.  They need very close accountability for a while to help them stay on the path of truth so they will not go back to the lies and habits they have believed in the past.  They also must stretch themselves and begin to be giving emotionally to others, especially the ones closest to themselves and not expecting a payback.  As children, the ones closest to them were the most emotionally dangerous so they have “labeled” ALL their closest relationships as dangerous.  This is a lie.
​

More understanding about Narcissism.

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If my people, who are called by my name, will humble themselves and pray
and seek my face and turn from their wicked ways,
then I will hear from heaven and I will forgive their sin and will heal their land.
​
2 Chronicles 7:14