Many people think that the sign of a good speaker is someone who never uses verbal ticks like “ah” and “um”. But, I disagree. The best way to judge a speaker’s impact is if that person conveys a sense of confidence. Audiences are swayed when they believe the speaker is confident. We all have verbal ticks. As long as you don’t have so many that the audience is counting you’re OK.
What really matters is that you look and sound like you believe in what you’re saying. If a few ahs and ums slip in while you’re talking, don’t let it bother you.