Define the behavior for your child. By explaining the behavior as clearly as possible, you will know that you are discussing the same thing. Specific examples can be helpful, but avoid using too many since this can make the child feel defensive. If the child feels attacked or threatened they are not going to want to open up and talk.
Ask child questions to help them figure out what purpose their behavior is serving. Questions like "How do you feel when you do it?" and "What happens before you do it?" can help. All behaviors have a function and determining what it is helps with finding a solution. For example, a child might hit people when they are frustrated because they feel they have no other alternative.
Develop an alternative behavior to achieve the same function as the unwanted behavior. For example, if a child is hitting people when they are frustrated, another option might be for them to go to their room to cool down. Your child should have a very large part of making this decision. Brainstorming different possibilities is a good way to get them involved.
Decide on consequences together. This is not just for the unwanted behaviors, but also to reward them when they do the new behavior correctly. An example would be having a reward chart where they get a sticker for each day they went to their room instead of hitting.