You've made the life-changing decision to leave your husband. Now for another hard part -- telling him. Exercising kindness and respect -- together with planning where, when and how you are going to break the news -- will make it a little easier.
Anticipate His Reaction
If you have discussed your marital problems with your husband, you should have a fairly good idea of how he will respond to your announcement. However, prepare yourself for a range of reactions from him, including anger, shock and denial. It may be a good idea to discuss it with a trusted friend beforehand, and prepare appropriate responses to things your husband may say. Resolve not to argue, and to remain kind, no matter how antagonistic your husband gets. If your husband doesn't want a separation, he is likely to be devastated -- don't expect him to act rationally. Brace yourself to cope with his distress. The best way to do this is to simply stay calm and listen, as nothing you say at this point will make him feel better.
Consider Time and Place
This important discussion should be held in a private place, with minimal risk of interruption. However, if you feel unsafe being alone with your husband because you fear he may react aggressively or violently, have the discussion in a public place and arrange to meet a friend immediately afterward. If you have children, make sure they are elsewhere. Don't have this important conversation if you are short of time, or just before either of you has an important appointment. You'll both need time to regroup and calm down afterward. However, do set a reasonable time limit if you anticipate an especially long conversation. Tell your husband at the outset what time you need to leave, and stick to this.
It's best to get straight to the point, but try to do it in a kind way. You may say something along the lines of, "This is difficult for me to say, but I owe it to us both to be honest. I have been unhappy in our marriage, as I suspect you have been too, and I have decided that I would like to separate." Explain the reasons for your decision, but avoid placing blame on your husband or making unnecessary accusations. Regardless of how he has behaved during the marriage, acknowledge your role and how you have contributed to the relationship -- and its breakdown. Tell him that you want the separation to be as painless as possible for both of you.
If your husband responds with anger or hurt, try to stay calm. He may shout at you, try to argue with you, or beg you to change your mind. Give him the chance to speak his mind, but don't get drawn into an argument or mud-slinging. Remember that he is hurting, and that there is nothing you can say or do that will make him feel better. If he doesn't want to separate, he needs time to deal with what's happening. You might consider staying with a friend for a couple of days to give him some space, later having another discussion about the details of how you will move on in your separate lives.