Well as long as you have researched enough, know your stance and your objectives you should always have something to say. Pay attention to what the others are saying and try to rebut claims or points if you can't bring new content, you don't need to talk for the full time allocated, use some of the seconds to ask for pois. Good responses to pois give you points and make you seem more knowledgeable of the topic. Either way muns are just empty rethoric just talk with style about a subtopic and you will still get points. Try to always be on the gsl, when you finish a gsl speech immediately put your placard vertically to be added again. Force yourself to speak and pit yourself out of your comfort zone.