Let's not pretend this will be easy or that any method is narcissist-proof, because most of you probably already know this is not the case. Anything that involves narcissists is difficult enough and trying to get them to co-operate on something or do something in the best interest of anybody but themselves is ridiculously hard. It's basically impossible, to be honest. So what do you do?
The first thing to do is approach this realistically. Forget what you've been told about co-parenting. That is a bold statement but that advice is written for normal people going through normal divorces or separations. You are not one of them. You are going through hell with a person who has absolutely no interest in making it any easier on anyone, including your children. In fact, they have a vested interest in making it harder. Realize this from the jump. You cannot get a narcissist to co-operate with you. You will only exhaust yourself trying, and you will give them ammunition against you in the long run. The narcissist is not your friend and they are not interested in working anything out. Don't be fooled and let that hope go. You cannot appeal to their good side. They don't have one. Not in this situation. Not when they are angry. If they have to hurt the children to hurt you, as you already know, they have zero problem with that.
Limit Your Contact with The Narcissist
You want to make sure you limit contact with the narcissist as much as you possibly can. You can't eliminate it totally, but you can minimize it. When you have to speak to the narcissist, try to do it in writing. Texts, emails, instant messages... these things are best. This way what was said cannot be debated and it can be proven later if need be. Write down all the details of meetings and visitations, so that if and when the narcissist tries to claim you did not allow them their visitation rights - or if they deny you yours - you have a record of the truth.
This is really important, so make sure you keep up with it. You might need it. Narcissists are known for trying to take the child away from the other parent. They do this to hurt the other parent and to establish control over the situation, not because they have any true interest in the child or the child's well-being. This is why you need to really stay at the top of your game, so that you don't make any mistakes that would allow them to do so. The court does not understand narcissists, and they go by proof. Make sure you have some. You have to protect your children and in this instance, that means protecting yourself.
Don't React to The Narcissist
When you do have to deal with the narcissist, make sure to employ The Grey Rock Method. The Grey Rock Method involves becoming a grey rock emotionally. You don't react emotionally to anything they say. This not only breaks the cycle and takes the power back from them, it stops them from having control over your life and your emotions. It gives control over your emotions back to you. This is so important and it must happen if you are going to heal from this relationship. However, be warned! As with anything else designed to take power away from narcissists, they often react very badly to this. Narcissists can be dangerous people and a narcissist who is losing power and control can be deadly. Prisons are full of them, and not enough "expert advice" takes this into account. Be careful.
Establish - and Keep - Boundaries
You want to make sure you establish very clear boundaries with the narcissist, both physical and emotional. If they break the custody agreement (and you really should have a legal, binding custody agreement), take them back to court so it can be enforced - every time. You want to send the clear message that it will not be tolerated. Don't engage in their attempts to provoke you in front of your child. Don't argue or defend yourself, especially in front of your child or out in public. Simply walk away from the conflict. Let the narcissist be the one standing there shouting horrible things in the middle of the soccer game or at Chuck E. Cheese. Even if it is killing you not to respond, control yourself and walk away. It's very important to stick to your boundaries here. Don't do it for you. It's hard and it's not fair, but do it for your child. Your child needs at least one parent that is not an emotionally abusive terror. Make it you.
When you speak to the narcissist on the phone or in writing, hold on to these boundaries. If the narcissist tries to bring up something not related to visitation or custody - even if it seems like friendly conversation - ignore it. Don't tell the narcissist your plans or your business unless you absolutely have to. Again: do not volunteer any information about yourself or your life unless it is critical to visitation or the children's lives. If the narcissist persists, firmly and politely let them know that you are only discussing the children and visitation, or whatever critical issue the conversation is about. If it is not a critical issue about the children, you should not be talking to the narcissist. If they are not OK with that, end the conversation, telling the narcissist that when they are able to continue talking about the subject only, the conversation can continue. If the narcissist has custody of the children or wants custody of the children, get a lawyer. If you can't afford a lawyer, get as much legal help as you can afford. Study and learn the law. Get proof of any and all abuse, including abusive texts, instant messages, proof of smear campaigns, phone calls, videos and anything else.
Don't Get Involved in Mudslinging
You want to make sure you never criticize the narcissist to the children or in front of the children. This can be construed as parental alienation and it's bad for your children anyway. Just try not to talk about the other parent at all. If you can limit the children's interaction with the narcissist while they are with you, that can go a long way toward defusing problems. You can monitor their interaction as well, by having the other parent on speakerphone or by reading the text messages. Ordinarily this would not be advisable, but this is not a normal situation. You have to protect your children and yourself. If you are aware of any abuse toward your children - this includes questioning them about you and saying horrible things to them about you - record it or document it somehow, then calmly let the narcissist know that what they are saying or doing is not appropriate for a child to hear or see, and you are ending the conversation in the best interest of the child. Then do so.
Narcissists see themselves as victims and they would love nothing better than for the children to see them as victims as well - of you. If the narcissist attempts to turn the children against you or otherwise disrupt your relationship with the children, this is child abuse. It should be documented and reported when it happens, and the interaction should be stopped to prevent damage to the child. Children should not have to listen to grown up problems and they should not have to hear what a terrible person their parent is. This is not OK, and it is a huge problem with narcissistic relationships. If this is going on, put a stop to it when you can, and make sure you document it to prove it to the judge or social services or whoever ends up getting involved.
Above all, be there for your kids. You cannot control everything that happens. All you can do is try.