The impromptu speech is unexpected and thus delivered without preparation. Some impromptu speeches are special occasion or courtesy speeches such as welcomes, Introductions and acknowledgments。.As this style of speech usually takes you by surprise, it is important to think clearly, analyze the situation quickly and speak briefly and to the point. As you talk, use the following order of presentation:
Clearly indicate the reason for the speech
Say why it is important to the organization or audience（你从即兴演讲开始就要直入主题，少说废话）
Conclude with some of the characteristics of the individual or organization receiving the recognition.
A successful formula used by many speakers for an impromptu speech is the PREP formula
P stands for main point （第一步先明确观点，你同意还是不同意，支持是否；典型句型有：I don't agree with the topic （重复题目）比如2006年清华大学曹峰的即兴演讲就是这样开始的）
R stands for the reason （推理自己观点的正确性，环环相扣）
E stands for the example （举例，举例是要求具体实例，不能假如问句，即使有问句，也是修辞的需要；你的例子必须通俗易懂，里面不能有生词，如果有，要解释这个生词，然后再继续你的例子）
P stands for restating the main point （首尾呼应，重新阐述自己的观点）
A speaker following this formula would start with the main point and then state the reason for talking to that point-for example, a long-standing commitment to an environment issue:
State the reason clearly. Follow with an example to illustrate the main point, to draw the picture and involve the audience.
Examples that add interest may come from your own experience, a friend's experience or a past experience common to the group.
Benjamin Franklin人名+american inventor and politician人的背景+once said）
Alternatively, you may use statistics or a relevant quotation. Conclude by restating the main point in different words.
This reinforces the main point and gives strength and continuity to the delivery. As you follow this formula, both speaker and audience reach the main point quickly.