Find a Good Lecture Topic

Before delivering a lecture on a specific topic, make sure your topic can be appreciated by the audience.

Steps

You have to keep in mind the average age of your audience members. Choose a topic that people of that age can relate to. Always remember to make your speech something that can be appreciated by all.
Pay attention to current events and note if something interesting has happened recently that might attract the attention of your audience.
If you are going to speak in front of an audience of a specific community, select a topic that covers their common interests. For example: If you are invited to deliver a lecture to the students of honors physics, you can choose a topic like Theory of Relativity or Thermodynamics, etc.
If you are going to deliver a speech to an audience that has people of all ages, then it is better to pick a topic that covers the knowledge of the lowest age limit.
Surf the internet to find information about the topic and collect diagrams, photos, etc. to spice up your lecture content.
Read articles and books on that topic to increase your own knowledge of it.

Remember to start your lecture with an interesting introduction that draws the attention of your audience.
Humor can play a great role in your lecture. But it must be limited. Sometimes the lecture can be excellent without going beyond the topic at all.
You can make your topic more interesting by adding some examples from everyday life.

Never choose a topic that can offend your audience. If you make your audience feel too offended, you may find only the chairs and desks to listen to your lecture.
Never speak in the same tone or use the same information twice. It makes the audience doubt your knowledge on that topic.