「哈佛大学终生教授，美国工程院院士，清华大学讲座教授。长期从事系统控制科学及工程应用研究，在最优控制、微分对策、团队论、离散事件动态系统和智能系统等方面做出了重大贡献」
My recent attendance at meetings in Xian and HongKong, allowed me to listen to many interesting talks and good presentations. As a student of giving talks and advice giver for making presentations, I am moved to make some observations on delivering talks.
People have caught onto the use of animation in PowerPoint slides. Many such use are impressive and effective. The general level of presentations have definitely improved in recent years. What I mentioned below are another set of details speaker and slide preparer should paid attention to so that they further enhance their effort.
1. Many speaker still put far more information and content on each slides with the result that they don't have time to explain all the stuff on the slide and cause only distractions. In fact, if you don't have time to explain what you put on a slide then the information should not be there on the slide! Put everything you can think of on a slide may sooth your conscience of being complete but you achieve the exact opposite result of confusing the audience. One should use this criterion as a test when you rehearse your talk. A necessary but not sufficient condition for a good talk is to be able to explain everything on the slides in the allotted time. I have said this before. Your job giving a talk is NOT to satisfy yourself but to make your talk interesting and understandable to the audience. There is no need to say everything you know in a talk.
2. Every math symbol, equation, and graphics you introduce in a slide of you talk should always be done BECAUSE you need to use them repeatedly. Not only this reinforces the shorthand notation but also minimizes content of a slide and explanation required. Otherwise there are no reason for their use except adding more confusion. Using symbols and equations may be rigorous and precise but unless done carefully their use only adds confusion. Your job is to be conceptually and logically rigorous in giving a talk but NOT mathematically rigorous. These two views of being faithful to your audience should not be confused. In fact, I'd argue that using too much mathematics in your talk is actually cowardly and taking the easy way out. Being understandable and conceptually faithful at the same time are much more difficult. But the effort is well worthwhile and will pay off for you in unexpected ways years into the future.
3. The purpose of a math symbol in lectures and writing is a SHORTHAND. When you have to express a concept or an idea REPEATEDLY, you use a symbol or a string of symbols (I.e. An equation) to save time/ words and to be precise provided the symbols have been defined previously. In a lecture it is difficult for the audience to remember many definitions once they have been introduced. Thus use symbols very SPARINGLY and ONLY when you are convinced that you will need them many times in the course of your lecture so that you can reinforce the definition and concepts.
4. The idea of careful use and reinforcement of symbols apply even more to graphics and animation. Yes, a picture is worth a thousand words. A carefully designed graphics reused several times in a talk with different detail animation or data can tell ten thousand words. That is taking the art of presentation to a new higher level.
Thus, in summary here, in my opinion, is a checklist for every prepared presentation:
1. Make sure you can explain EVERYTHING you put on a slide in the time allotted . In general use no more than two minutes per slide => about 15 slides for a 30 minute talk.确保在预定时间内你可以解释所有你所放进PPT的东西。（解析:一是时间观念每张分配多长时间，一张不要超过2分钟，一个报告在15到30分钟为宜，二是你放的即你懂，要都能当场解释的清楚）
2. Use symbols, equations and graphics only when you are convinced that you will use them repeatedly in your talk. They need to be reinforced.解析:只有当你确定你在演讲中会反复用到某些符号，方程，图表时，才放在PPT上，此时为了突出某个符号，方程，图表的重要性，不得不解释，才放上去，一般不要在PPT上放，演讲PPT更多关注的是逻辑自洽，讲好这个故事。
3. Prepared your talk from the viewpoint of the audience. Think how they would like things explained to them.解析:有同理心，假设你自己是台下的观众，希望那些东西如何被解释才最被接受？那么就按照观众的眼光去准备你的这个演讲。
4. You should always start preparing and rehearsing your talk weeks in adavance. Improve and memorizing it to the point that you only need the PowePoint slides to help you deliver the talk.解析:公众场合演讲最好提前把PPT背熟，在正式开始前反复演练，PPT只是帮助你更好地传达你所想表达内容的媒介，照着念会被人瞧不起的，早点下台免得耽误观众时间。
