Randy Park
Thinking for Results

i am increasingly convinced by emigre's assertion that typefaces are not intrinsically legible; rather, it is the reader's familiarity with faces that accounts for their legibility...

of course, there are limits to this, but if i were you, i would print out your text in a number of typefaces, sizes and line spaces, and see which ones you find the easiest to read in a 'lectern' environment

general rules would be generous line spacing, not more than 9 words to a line, and clean, open type

type that has proved popular when i have provided templates for friends who do a lot of public speaking include palatino, georgia, frutiger, myriad, officina and minion...

I think the legibility issue is far from decided too. Saying that, one factor is certainly line-length, rather than choice of typeface or even size. Taking legibility as a factor inherent in a typeface, (certainly some faces are less legible if not the other way round) maybe something designed for screen might be useful to work out where you are at a glance, even if it looks a bit nasty printed. Big bowls, short ascenders/decenders.

Mildly (un)connected, there's a story about London Transport testing whether dsetination boards in all caps or initial caps were more legible on London buses in motion and at distance. The tests were performed in the early 20th century. I think it was entirely inconclusive and neither way was more legible than the other. Factors like size and contrast were more important. Today London buses use yellow on black with initial caps. In Johnston of course. I'm not suggesting this it's good to prepare your speaking notes this way though.

If you are teaching about communication, shouldn't you not be reading from a script. Maybe just note cards. The most important thing is to connect with the audience which means eye contact. No?

I agree with Brett. Especially in this instance. You just need something with a large x-height and open shapes.

"I was surprised not to find anything definitive on the web (just “use a big font”.)"

That is because, in such a case as this, composition is the key, here represented by the word 'big font'. That is to say, 1,000's of fonts will work just fine... if the one chosen is thoughtfully composed. Details of stroke, serif and width are all subject to the composition of good line length, leading and, in the case of presentation, bulleting sentences where visual interruption of the reading is likely.

Cheers!

Right Tiff, I speak mostly without notes, but do pause occasionally to decipher scribbles on scraps of paper.
I find the process of writing aids memory better than typography, in forming a gestalt image of the way the thoughts are arranged on the page.

Yeah, composition is the key.

What about emphasis on key words on the text so yo don't get lost?

Héctor

Randy, I agree with all of the above.

Because of the reading method, I'm not sure that serifs are really that important as long as you choose a typeface that distinguishes confusing characters (cap I vs. lowercase l, for example) and aids quick recognition of character shapes. Signage fonts (humanist sans are often chosen for this purpose) may be a good bet. Web fonts (such as Georgia) might work well, as they are designed to be pretty simple and robust for the screen. Uniform strokes could be good, but a mono-line might not distinguish characters as well as something with a bit of stroke variation.

But, as David points out, you're spoiled for choice when it comes to fonts. It's the layout that's crucial and more specific to the task. The font will fail or succeed because of it.