First see that when you are on stage you should not not feel that you are speaking in front of audience instead you should feel as if you are performing on an empty stage if it's for first time just believe in your self don't think or worry about others

for speaking fluently you must speak a bit slow for understanding of what you are speaking and you even get time to think of what you are going to speak
use simple words
avoid aah etc between your speech
pay attention to your pronunciation
your expressions and your way of speaking

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Trust that no one is going to slap you for your performance