If you have direct eye contact with people during the discussion it will show that you are confident in your answer and people will also be confident in your answer. If you talk loud then people know that you're confident in your answer, but if you talk low then people will think that you aren't confident in your answer. If you have clear pronunciations then people will understand what you're saying. Lastly, if you have a good speaking rate then people will understand what you're saying and believe what you're saying.
