Be positive, not negative. Second, the partners discuss the details of their disagreement. It's important that feelings about the specific issue come up, but not about old issues. Third, the couple negotiates until they can agree. Sometimes all they can agree on is that they disagree.
Negotiation includes give and take.
You clean it. Then there is no give and take. One common mistake is denying the other person's feelings. If possible, admit that you might be wrong or might have done the behavior you're discussing. You'll both feel less defensive.