To be a good debater, one should make their point in a persuasive manner. The most persuasive arguments are ones delivered with confidence and that have evidence to back them up. However, the debater should also be respectful of the person they are debating. They need to listen and be open to counter-arguments while maintaining their position. Confidence, evidence, respect, openness, and even a bit of stubbornness, so to say, are all elements of an assertive communication style, which is why using such a style can help you be a stronger debater.