Being right is the smallest part of it. Rooms are not won by the better argument; they are won by the argument that arrives intact, on time, in an order the audience can carry home.
Know the shape before you fill it. Every format decides in advance where your strongest material belongs, and the speaker who has not read the structure spends their best minute in the wrong slot. Where rebuttal sits, whether you get the last word, how long the last word is allowed to be — all of that is settled before anyone speaks. Read it. It is usually one page.
A four-minute point delivered in three minutes is a good point. The same point in five minutes is a liability, and everyone in the room knows it before you do. Practice against a clock until the clock stops surprising you. Then build in the thirty seconds you will lose to the thing you did not anticipate, because you will lose them.
The most useful skill in competitive speaking is cutting your own material while standing up. It is learnable. It is also miserable to learn, which is why so few people do.
Agree on the signals before you go in, and keep them to three: time remaining, slow down, wrap up. More than three and your partner is translating instead of listening. Signals come from one person only. A speaker checking two sources at once is a speaker who has stopped arguing.
Everyone asks this and almost nobody gets a straight answer, so: rest them on the lectern, at the top edge, wide enough that your shoulders stay open. Move them when you mean something. Return them to the edge when you are done meaning it.
The failures are pockets, which reads as reluctance; gripping the sides, which reads as fear and is visible from the back of the room; and constant motion, which reads as nothing at all. Hands should punctuate. They should not narrate.
You are not trying to be unanswerable. You are trying to be the version the room repeats afterward.
Phone audio from the back of the room. Tell us the format and what went wrong last time.