| I'm always surprised by the amount of advises in rehearsal. I like to give public speaches, but I organize myself completely differently. I spend much time making Slides that are easy to follow and logically ordered, and in each I know that I can say a little more or a little less without disrupting the message. I know that I can count on 1 slide = 1 min. Unless lots of images. I don't rehearse as I know that I prepared well my slides. Then during the talk I add more or less informations naturally depending on the time left and on the facial expressions of the audience. I usually finish exactly on time. Usually I read my slides and think about what exactly to say only just before the talk. I find this way more natural, and less scripted, and I usually get compliments on my presentation and naturalness. I think rehearsing removes much of the naturalness of a talk, unless that aspect is worked extensively, but that could sound a little too scripted for my taste. One trick that I use often if I tend to forget some information that is important to say, is to put one word that trigger the information IN the slide, but in very light Grey, and in a natural place, like close to an image. So if I ever forget what to say, I have my landmarks in each slide to guide me. |
All this is not great for the audience (who have "invested" into your session, by paying for the ticket, spending time away from work and family, not attending other concurrent sessions, etc.), and it can so easily be avoided by rehearsing.
The most common reason I have seen for folks skipping to rehearse is the awkward feeling you might have when speaking loud all by yourself. If that's the issue, it can help to do a dry run in front of colleagues. In any case, "winging it" is best reserved for later on, after having gathered quite a bit of speaking experience and having spoken about the same, or very similar, topics before.
I'd also recommend to avoid reading from slides during a talk as much as possible, it's also not a great experience for the audience. There shouldn't be much text on slides to begin with, as folks will either read that, or listen to what you say, but typically have a hard time doing both at once.
(All this is a general recommendation, not a comment on your talks which I have not seen)