In 11th grade, I took Rhetoric I. One of our first assignments was to memorize and deliver Shakespeare's St. Crispian's Day speech. Here was the catch: we were told when we had to be ready to present, and from then on, we could be called upon to deliver the speech at any time. In the cafeteria. In chapel. In another class. During our class, but taken to give it to another class.
As soon as Mrs. G. passed out the speech, I vowed to have it memorized at least two weeks before the delivery date, so that I could focus solely on my delivery for a while. My trick? Read the speech out loud to myself every night right before I went to sleep. The brain transfers short-term memories into long-term memories while you sleep, and it transfers LIFO, to use an accounting term, meaning Last In, First Out. Whatever you last put in your short-term memory most recently will be put into your long-term memory first. I wanted to take advantage of my brain's work and make memorizing easier.
This trick worked! I had the speech memorized early and was able to focus on a strong delivery for a longer time.
In Rhetoric II, we got to select a historical speech to memorize and deliver. I chose President Reagan's speech he gave on the 40th anniversary of D-Day. It was a great speech. Again, my trick was to memorize it really well and then focus on delivery. I have an advantage in that I am an audio learner, so reading it out loud helped me both memorize and practice delivering it.
In both of these situations, my instructor allowed us one 3x5 note card on which to put notes for ourselves. What helped me was to have an outline on one side and then one or two "sticky" sentences fully written out on the other side. I knew the speech well enough to just go by an outline, but there were usually one or two sentences that continually tripped me, so I wrote those out and would read from the card when it came to those sentences.
A delivery trick I use is to have one of my friends sit up front so I have someone to make eye contact with often and to see her smile and nod as I make it through the tough spots. Also, when looking out at the whole audience, I look above their heads. Just barely, though. Skim their foreheads with your eyes so that it looks like you're making eye contact but your nerves don't jump from actually seeing people looking back at you.
Hopefully these tricks that helped me will also help you!