Constantly educate yourself with something new. New things are the best training for your mind, and keep it sharp. Remember a book from school years which was forced you to read by a teacher? Try it now. You can always give up reading it but try. You'll be amazed how different the content is after 20, 30 or 40 years. The reality is that the content is the same. You are different. Try this with books, music, theatre, movies, take the topic you have never touched in your life. By doing this, you'll train your mind and develop as a speaker in very different fields. Sometimes I am amazed how tribal folk knowledge helps me when dealing with the energy sector with media ;) Alfred Jarry was a French symbolist writer.