A debate is a highly structured argument on an agreed topic. It is usually argued in teams. Two sides speak alternately for and against a "motion," moderated by a chairperson. Each speaker is allocated a particular length of time and interjections are carefully controlled. Outside Parliament, which is based on a debating system, debates are usually held for entertainment or for educational purposes. If you are writing a debate speech, you may have been asked to defend a point of view that you do not yourself hold. This is part of the fun.
Writing your speech
Prepare a formal greeting. At whatever point in the debate you are speaking, always acknowledge the Chair and show respect to your opponents and guests.
Outline your central thesis, or argument. State which side of the debate you are on and explain the general thrust of your case. Keep it brief, clear and compelling. If you are the first speaker, you may wish to introduce the arguments that other team members will be using. That is something that you should discuss between you beforehand.
Separate out your supporting arguments. Go through each argument, one at a time, and write your script. Use statistics, facts, and measurements where possible to support your case. Stories can also be effective.
Use a variety of rhetorical devices to bring your speech to life. These can include rhetorical questions, similes, humour, irony, and the "reductio ad absurdum," which is a way of ridiculing your opponent's arguments by taking them to extreme lengths. For example: "My esteemed opponent suggests compulsory euthanasia at 70. I ask, why 70? Why not 60, or indeed 50? If you have children, they have grown up by then. If not, frankly, you'll never have them, so what do you have to live for?"
Wherever necessary, do not be afraid to acknowledge your opponent's arguments. This will make your case seem all the stronger. For example: "Yes, conducting a complete overhaul of all our roads would be expensive. But it would yield far greater returns."
In conclusion, restate your thesis clearly. You may also want to include in your script a brief thanks to everyone for listening.
In a debate, you should use any verbal weapon you can think of to demolish your opponent's arguments, but never attack him or anyone else on a personal basis. It will lose you sympathy.