Q
What do you do when your child hits and screams at you when you try to discipline him?
A
It would help if I knew what the age of the child was and what you are attempting to discipline him for when he acts this way. I am going to assume this is a young child we are talking about and my answer will reflect that assumption.
Disciplining a child while he is throwing a tantrum and/or hitting and screaming is impossible, so don't even attempt it. Say to the child in a firm voice, while restraining him from hitting you if he follows you around, "I know you are very angry and out of control now,don't hit me because you're hurting me and making me unhappy". Let him have his screaming fit, remove yourself physically from him and do not allow him to hit you.
Discipline should provide the child with natural consequences, not punishment, for his actions and should be given when both of you can hold a peaceful conversation.