Sarcastic Lectures

When it comes to lectures they are some times very difficult for me to give because most of the time I have ideas running through my mind. For example if im talking to soft or mummbling alot, it just gets so nerve racking. Also in the back of my mind I alway have the idea that my thoughts are pointless and wrong, and why are they listening to me.
I recall how there was once a lecture I had to give regarding Chicago for my final project for middle school. The project me to stand up in front of my Socials Studies class and talk about the major landmarks of Chicago and its history. The Lecture didn't start out so great because I kept thing maybe my information was wrong or even if I had enough information. Then near the end people started asking questions and the way I answered was in sarcastic funny ways and it really broke up the feeling of nerviousness that I was having before. Even since then when ever I do a lecture I act alitte sarcastic and it breaks the tension.