Watch the words that you say. Using tentative words like "I think, maybe, might, should, could," or alternative words can lead people to believe that you're not confident about what you're talking about. So confidence comes from experience and knowledge, but using the right words and avoiding other words help you to be more confident.
When you're speaking to a group or to someone. The word you say truly do matter and being confident in the words that you say helps the right message come across. If you're in sales and it's important for you to to have customers believe and know what you're saying is true, then watch the words you say.
Watch words in your vocabulary. Be confident, be dynamic, speak with passion, and speak with inflection, to improve the delivery of your message. Be confident and choose the right words and watch the impact you can have and models the way for others.