Bragg, L., "The Art of Talking about Science," Science, Vol. 154, pp. 1613-1616, 30 Dec. '64
The following quotes are excerpted from Bragg's article. Although the author considers the one hour lecture, and focusses on science, much of what he wrote is universal.Most undergraduates are much more concerned with what they need to do, and how to keep the talk relevant. Often the last word means "similar to the content of their very technical curriculum." An antidote for that viewpoint's excesses is found by reviewing excerpts from  that appear below. Some tips on preparing a talk are with the text of  at Bragg's article
What is the basic character of a "talk"? I think it can be expressed by saying that its primary object is to create a state of mind, or point of view, not to convey information.
One need not cross all the "t's" and dot all the "i's". In fact, the talk would be spoiled by an attempt to do so.
A talk is different from a "paper". The success of the way in which the subject has been presented is measured by the extend to which the average member of the audience remembers it the next day.
I like to compare the composition of a lecture to that of a picture. ... The force of the impression depends upon a ruthless sacrifice of unnecessary detail.
The essential feature of a lecture is the emotional contact between lecturer and audience. If a lecturer has to find his words as he speaks, he will be automatically restrained from going fast because he is thinking along with his audience.
A lecture is made or marred in the first 10 minutes.
The audience can follow at about the rate one can draw; one is forced to be simple, and the slight expertise of the drawing holds attention. One must constantly think of what will be retained in
the audience's memory, not of what can be crammed into the lecture.
A lecture is a tour de force and a good and conscientious lecturer is both nervous beforehand and prostrate afterwards.
Every lecture must be approached as if it were a new problem. No pains are too great in the attempt to make a talk a success and I believe that given the right treatment, any subject can be made fascinating to any audience.