Answer:
A main idea, key details, and understandable language.
Step-by-step explanation:
Without a main idea, well... there's no point to your debate. You need to make it clear what you're arguing for (aka what side you're on) so your audience and opponents can grasp the gist of what you stand for. Key details are especially important because you can't make an argument without evidence. That would then be a baseless claim, you always need accurate specifics as to why your idea/side is the better option. Lastly, understandable language is always important because a debate is verbal and your judges/opponents need to understand what you are saying in order to fully comprehend what you're advocating for.
The ultimate goal is to persuade and get your point across.