As part of my work, sometimes I need to memorize some speeches or some presentations and in order to do that, what I frequently use is one technique called: Memory Palace (which originally comes from an ancient method called Method of Loci).
The approach of this technique consists on basically breaking down your speech into the main concepts you want to talk about and you try to look for a visual image for each of the concepts. It is very important that you have a vivid image for every concept you want to memorize because it will be much easier to retrieve it from your memory later. Once you have all your images, you mentally place them in a place that you know perfectly that we’ll call your “memory palace”.