One of my favorite memory techniques was actually used by the Greeks over 2,500 years ago. It's called loci, for location. Also, some people refer to it as memory palaces. One of the best people to teach this technique is a guy named Jim Kwik. K-W-I-K is his last name. You should absolutely look him up. He has a great podcast and he teaches this. This is how I learned it, from him.
What he teaches us is to take a room in your house, any room you want but it's got to be a room that you're very familiar with. What you do is you attach your talk to the room. Sounds crazy, right?
Here's what you do: You take pieces of your room, sections of your room or objects within your room and you link them to ideas within your talk. Let's say your talk opens up talking about the future of our planet. You might link that to your front door because when you open the front door, your future life is within your home. When I open my front door to my house, the first thing I see are the stairs. The stairs might symbolize in your talk that there are endless possibilities because the stairs can go on forever and ever.
What you want to do is walk around a room in your house in a clockwise direction and attach a part of your talk to each section. I use this technique in every talk I do now. It really helps because say you're in the middle of your talk and you want the talk to be amazing and you're thinking about what you're saying and what you are going to say. You think, "Where am I? Fireplace. What comes next? Orchids, right. Orchids symbolize growth and I'm talking about growth here. Got it! Done."
The audience will never know what you're doing. But for you, it's a wonderful memory device because you cannot get lost in your talk. You know exactly what comes next. Maybe there's a map in your house and that symbolizes discovery, something that you're discovering in your talk. Maybe there's a chair that symbolizes comfort. You can attach any section of your talk to anything in your house as long as it has meaning. You don't want to place a part of your talk about adventure on a table if that table has nothing to do with adventure. If you have a book on adventure or travel on your table, perfect. Attach it to that book, because that will help you remember.
Try this technique. Look up Jim Kwik as well! I guarantee you this will have a transformational effect on your talks in the future.