How to Start an Introduction for a Debate
Research your part of the debate. Say for instance you are arguing for stricter gun control. You should already have your statistics on gun ownership, reasoning for stricter controls and what benefits that should have, and counter arguments against your opposition's likely points prepared before you sit down to work on your introduction.
Examine your points carefully. Your introduction should take the best points you prepared in your debate, without actually using them up front. For example, if you were opening a debate for gay marriage on the pro side, you should mention broad points, such as the idea of equal rights. You should not include specific numbers in your introduction.
Write your introduction. It should include a statement of your purpose and view on the debate, as well as list broad, persuasive points. The language used should be appealing to your target audience, and your introduction should be as brief as possible, taking no more than 20-30 seconds to read aloud.
Test your introduction on a target audience. Find someone outside of your research and ask them to read it, or to listen to you read it. Ask them for feedback. Find out what parts of the introduction work, if the language is right, and if the tone is proper. Then revise your introduction, and try it again.
Once your introduction has been revised, revamped, and tested on other people, it's ready to be read. Care should be taken that every part of your debate undergoes the same treatment as the introduction, otherwise your audience will be sucked in by a false promise.