1-Before discussion, know what do you want from this discussion: know what do you want from this discussion, what consequences do you want to achieve, what is your information and if it enough or you want more information.
2- Define key issues and areas of interest: try to write the points that interest you and the points that interest the other person and give yourself enough time to study the issue.
3- Avoid getting into a sterile argument: do not turn the discussion to useless argument, do not start or continue the discussion if you find the souls angry, wait even the things calm down and absorb the anger of the other person without insulting yourself.
4- Ignore the attack and talk by Facts and evidences: do not put yourself in the position of self-defense so ignore the attack and talk by evidence.
5-When the other person gets out of the subject of discussion: if the other person does this, ask him a question which restores him to the subject of discussion or ask him clearly to come back to the subject of discussion.
6-Look at the things from the other viewpoint: if you try to understand the other person, you will find that there is a hidden reason for his situation. When you know this reason, all cards will be in your hand and you will build your thinking on a right basis.
7- Let the other person talk: the best way to maintain the power of your situation is to let the other person talk and say his viewpoint. Do not interrupt him.
8- Find out the Points of agreement and disagreement with the other person: search for the points of agreement first and when you find it start your talk with it. When you find the points of disagreement, try to find out why are you differing with him?
References: Be Professional in Talking and Persuasion- Ibrahim El-Fiqy.