Don't focus on only one person or area.  Make eye contact with members of your audience. If eye contact is too intense for you, look just above their heads at a point such as a clock or a painting. Remember to look to both sides of the room. Don't favor just the right or left. Move your eyes around your audience so that everyone feels included in the presentation. The natural adrenaline rush that you will have in front of your audience may make you want to speak much too quickly. And have a confident smile on your face. If by chance, you forget your speech, then simply say thank you and leave the stage. Your audience will find you much more easy to relate to, and you won't lose their confidence in your knowledge of your subject. Never leave the stage if something goes wrong, even if you feel embarrassed. Make a joke if you can, shake it off, and move forward. Ask questions. As well have them ask you questions, so you can touch up on some points that you overlooked and/or left out,)before leaving the podium at the end of your speech. Acknowledge your audience with a smile, a brief nod or a slight bow, if appropriate. Be sure to build time for any Q and A into your allotted presentation time. That way, you can control the flow of the Q and A. Then, after the last question, let your audience know, "I'd like to share one final thought with you," and deliver a powerful closer.

TL;DR in Chinese:
看看周围的观众，不要只关注一个点。 慢慢讲，尽量正常呼吸。 如果出错了的话就自嘲。 在演讲结束时离开讲台前，头脑里数5个数。