Typography is probably the biggest thing people fuck up.
Look. If you’re using slides during your talk, they should help you out, not fuck everything up. I have seen more slides that look like this than I have heard jokes about my hometown of Fargo, North Dakota (and I have literally heard all of them, yes including your clever woodchipper joke, although yes, that one is my favorite too):
No one in the room can see this- even the brown-nosers in the front row. Remember, most projectors you’ll have to use are going to be terrible, most people will be a minimum of 15 feet or more from you, and people at the back could be hundreds of feet away from you. Miles, maybe. Kilomiles, for those who use the metric system.
Here’s all that you need to know: you can’t go too big, use a ton of contrast, don’t use many words, and choose a solid font. More than anything else on this entire site, doing those four things right will put you in the top 10% of speakers out there. People fuck this stuff up all the time.
You can’t go too big
You really can’t. I have yet to see a talk that made me think “goddamn I can’t read this because the text is too big”. If you string together four projectors and combine them into a mega slide you still can’t go big enough.
I wish more people would build their slide deck from the audience. That is, sit in the very back of the room, hook up your laptop, and write your slides. If you can’t see what you’re actually doing from back there, neither can anybody else. You’re at a severe advantage when you’re a foot away from your screen, clicking away.
You can’t go big enough. Instead of this:
…you can do this:
Did you catch what I did there? It was a little subtle, but I bumped the font size up slightly. Remove words, make it bigger. You don’t always have to take up the entire slide, but the thing to note is that you can’t go too big.
Use a ton of contrast
Remember my first example that makes me want to commit felonies?
Dark green on black is horrible because it doesn’t have a lot of contrast. This is especially important because again, the projector you use will probably be terrible, and the room you present in will most likely not be a pitch black darkroom. Unless you combine a strong dark color against a strong light color, you’re going to have a hard time getting your audience to easily see what you wrote.
Black and white is usually a safe combination- it’s one of those things that it’s hard to go wrong with something so basic. And that’s a good thing. Otherwise, look into how you can select good colors and design that looks a bit more interesting.
Don’t use many words
Remove words, make it bigger. It’s a good policy to have. Part of designing a good, legible slide deck is to reduce the amount of things on your slides as much as possible.
That does two things for you: it makes it easier for your audience to parse (which makes it more valuable to you), and it also means less time spent reading for your audience. That’s good for them, because no one actually wants to read anything in life unless it’s 50 Shades of Grey, but it’s most helpful for you, since it means they’ll spend more time listening to you. You want your slides to accompany your talk, not be the focal point.
Choose a solid font
There are a lot of good fonts to choose. It’s actually a fairly minor thing compared to the other three aspects discussed here, but it can make a difference.
Usually I’ll try to pick something that looks clean and obvious at large font sizes. Sans-serifs are often good choices, although serifs can work as well… it all depends on how you use them.
If you’re looking for something a bit different than your computer’s default fonts, try Google Fonts. They have a slew of choices and a clever interface to help you narrow down what’s interesting to you. Other really great sites include the Lost Type Co-op and The League of Moveable Type.