Of course, all speeches has to be prepared.
Thought out, pondered, again and again, first.
Then told out loud, if possible to a dictaphone so one can listen to the result.
Written only then, most of the time, but sometimes, I tell it again to record a better version to listen.
Listen listen listen again and again. Imagine the scenes, imagine the content.
Learn the begining, the end and the important phrases of the speech by hart.
Before my Humorous Contest speech, Dare to Share, that I did put at the first note as I remember well, I did also buy myself a cheep video camera - and now, I am not sure where I put it one day when I was not happy about its resolution. But it was useful, and I'll find it again.
To test the camera I begin to repeat my Dare to Share speech. I did not realize then the importance of "dress rehearsal" which jumps to me now as I look at it, first. But it is an example of the begining stages of the speech. Telling it to my family, to my friends, I realized which part made them laugh more, and put it at the begining, as usually once they start lauging, they laugh more easy after it.
As it was told here, it was nothing to laugh yet in it. But yes, repetition, improvement, repetition, is necessary. I did not learn it word by word, but I knew it. Mostly I knew what I wanted to say, and with time, my movements improved too, as did probably my voice variety.