Know your numbers.
Whenever you talk about anything always quote the numbers.
Say 2 out of 20 people have this or that…, 60% of children are this or that…, et cetera.
Have your facts right.
Know what you really know, what you just have a clue about and what you don’t know.
In connection to that, treat all unconfirmed information as rumors and take an effort to research and confirm that bits of knowledge that interest’s you.
Be fast to acknowledge what you don’t know or just shut up.
Tell a story.
If the discussion is about a relative topic, package your point in a story.
Tell it so well that even if someone doesn’t agree with your point, they at least agree with your story; and trust me, you have convinced them already.