Let your mind wander as you search for topics. Do not simply do the same old thing old thing others have done before. Start with something that interest you, then start to keep a list or do a mind map other things that topic may lead you to think about. From that list do another list, expanding one or two of those "branch" ideas into specific aspects of the topic. Once you have narrowed the list down to something you really find interesting, start to work on research, creative execution, outlining and presentation. Feel free to change, shift and improve as you move through the speech preparation and presentation process.
One way to approach this process is to start with your pet peeves. what annoys you? what gets you mad? What would you change if you could? Make a list. Next, make a list of the ins you enjoy. What makes you happy? What brings a a smile to your face? what can you share with others? Still another way is to think of where you have lived, cultures you have experienced, things that have happened in hour life.
If you use the brainstorm list and selection process explained above you will be able to find a subject that is new and interesting to your listeners and that you will enjoy sharing.