While there are several situations where impromptu speaking skills can be utilized, here I will briefly discuss how to approach preparing for a five minute impromptu speech on an assigned topic.
Frame Your Issue
Start off by explaining what the issue is. Frame it in a manner that will put your arguments in the best light. (you might consider fine tuning this after you have come up with arguments)
Give Two or Three Reasons Why View the Issue the Way You Do
Before you dive into your arguments, briefly list what your arguments will be. This “roadmap” will give your speech structure both in your head and for the listeners.
Present Your Arguments
Then move on to presenting each of your arguments. In doing so, think about ways to best support each argument. For example, when talking about a legal issue, comparing past cases is where we would likely start when supporting our arguments. But we could also give policy reasons, share personal stories and make common sense observations.
At the end, remind the listener why your arguments are the best way to view the topic.