Hi there, I was a speaker on the debate team at my high school and did fairly well at the national competitions in Singapore in World Schools style debate. It’s challenging to improve your debate style on your own without feedback from a good coach, but one tip that I found really helpful (if a little cringe-worthy!) is videotaping yourself while you speak on the debate floor and then going over the video later to spot when you fumbled or didn’t make your point as clearly as you could have. Seeing how you come across will also give you an idea about how to improve your style, pacing and other factors that make your delivery effective.
Familiarity with common debate topics and arguments can also be built up by looking through past debate topics and practising coming up with case lines, arguments, examples and rebuttals for the most common arguments. This would help a lot in making you a better debater when you’re given a debate topic only a few hours or even minutes before you have to take the floor.
Logic and clarity of thought are also incredibly important for debaters to master, especially when it comes to rebuttal making on the spot. Reading up on and memorizing logical fallacies and how to spot them can be really helpful, as well as thinking up a structure for your arguments.
Reaching the national level of debate is tough and will depend a lot on how you measure up with other debaters your age in the competition, as well as luck, contacts with the national coach, and your performance on the circuit at the most prestigious competitions in your country. While it’s important to brush up on your speaking skills it’s also good to be strategic about which competitions you enter, what teams you go in with and whether you are getting the exposure you need for the national coach to be familiar with your work and so select you for the team. Could I ask which country you are based in? This may vary from country to country. I know that in my time in Singapore this was how the national team was selected.