Build your viewpoint on facts – Anyone can have an opinion, however if you can base your views on credible facts and information it will be a lot more solid. Think of expressing your viewpoint like building a wall with each fact like a brick in the wall. The more bricks you have the more sturdy the wall. Building fact upon fact can be even more effective than scattering a bunch of information randomly
Nonverbal communication – Your volume, your tone, eye contact, posture and hand gestures can help make your opinion easier to follow and more persuasive if used correctly. Try to exhibit poise. (Poise - a dignified, self-confident manner: composure, stability)
Avoid absolutes – Words like “never” or always” can ruin the credibility of the point you may be trying to make. It is good to be specific rather than make sweeping generalizations
Respect – Avoid being offensive or insulting. Usually once you insult the person you are expressing yourself too that usually shuts down any hope of coming to an understanding.
Focus on building up rather than only tearing down – It can be useful to point out some reasons why you disagree with a belief or viewpoint. However, if all that you can bring to the table are reasons why you feel that other viewpoints are wrong but you cannot make a positive case as to what is good about your viewpoint then you really don’t have a leg to stand on. For example if you were in a discussion about why you thought one sports team was better than the other you need to be able to explain why you believe your team is good instead of only bringing out why you think the other team stinks.