Overhead Projectors

Advantages of the Good Ol' Overhead Projector

The information can be projected larger than flipcharts and chalkboards, which means you can use them with larger audiences.
You can prepare them in advance (rather than write information by hand on-the-spot).
You can highlight information, circle or underline items, fill in blanks, etc.--then wipe clean and reuse.
You can photocopy articles, illustrations, charts, etc., onto a transparency.
The room lights can stay on. That enables people to write notes more easily and to see you, the speaker.
You can change the order as you speak, or even skip transparencies. A lot of flexibility.
Overheads come across as less formal than electronic slides, videos, and multimedia presentations.
You can print transparencies from your laser printer. You can even print color overheads from an inkjet printer.

The speaker reads what's on the screen.
The speaker copies small writing onto a transparency and reads from it--and few people in the audience can make out the words.
Since overhead projectors must be placed at the front of the room, they usually block somebody's view.
They typically project a distorted image--the "keystone" effect, in which the top of the image is larger than the bottom.
They don't work well with large audiences.

Turn the projector off when you're not using it so the bright light doesn't distract people, or put a blank sheet over the surface to darken the screen.
Make sure you have a spare bulb and know how to change it.
It's easier for people to focus when you're standing beside the screen, rather than beside the projector. They don't have to shift their eyes back and forth between you and the screen. Have someone else change transparencies, or just walk over and do it yourself.
Don't talk to the screen, unless you're pointing out something important. People will look where you're looking. If you shift your gaze to the screen and perhaps point at something, they'll look in that direction.
Mount Transparencies in cardboard frames, which you can buy at office supply stores. Write a number on each frame, to keep them in order. You can also write notes on the frame.
Tape an L-shaped guide onto the top of the projector just outside the lighted area. Use it to position overheads so they are centered. That way, when you begin a new transparency, you don't need to keep looking back and forth between the projector and screen, trying to get it positioned right.
Use a pointer, and point on the transparency itself. A chopstick works well. Don't use your finger as a pointer; it's too thick.
Overhead presentations work best with groups of less than 50 people.

In general, use the same design principles given under "Electronic Slide Design."
One major difference: Use dark type on a light (or white) background. With electronic slides, it's the exact opposite--light type on a dark background. When a room is fairly well lit, it's easier to read dark on light.
To test how easily it can be read by the audience: place the transparency on the floor. Stand up. If you can't read the information, the letters aren't big enough.
The best overheads use color sparingly. Don't think that just because you have access to color, you must use it.
Print your overhead onto white paper from a laser printer and take it to a quick-print place, like Kinko's. They have special copiers which can print certain parts different colors. For instance, you could do the headline in blue, a few key words in red, and the rest in black. It doesn't cost much.
Rule of thumb: make letters at least one inch high.