This article has been adapted from an article called "How to manage presentations" that was originally published in InteracTive magazine.

Think about colour schemes. People who are colour-blind will probably not be able to read any of your green text on a red background. A recent presentation I attended used black text on a navy blue background. It was illegible 3 rows back from the front.
Think about the size of the text. Letters should be about a centimetre (approximately half an inch) high for every 3 metres (about 9 feet) of floor length. In other words, if the room you are using stretches back 6 metres, your letters need to be about 2 cm high for anyone in the back row to be able to read the text without straining. Whatever you do, don't simply import a page of closely-typed text into a slide: there will be no point, because it will be illegible.
Think about the purpose of the presentation. The format and effects used should support the message, not take over from it. If your audience is thinking about what the next effect might be instead of what you're saying, you might as well pack up and go home.
Check the technology before the presentation is due to start. If that is not possible, because you follow directly on from another speaker, try to arrange for there to be a 15 minute tea break while you set up and check things. It is bad manners to fiddle about while people are waiting for you to start: their time is at least as important as yours.
Always have a backup. If the display unit freezes up just as you start your talk, you should be able to switch immediately to an overhead projector with the minimum of delay.
Think low-tech. If you are not sure of the facilities that will be available, produce your presentation on PowerPoint by all means -- but print it out onto overhead projector transparencies. At a recent conference, I witnessed 3 system breakdowns during presentations.
Have print-outs of the presentation available. If you print the slides in Handout mode, you can squeeze a 12 slide presentation onto a double-sided photocopy. If you print the slides using the "with notes" option, each slide is accompanied by blank lines that people can make notes on. If you can't afford the printing costs, make sure there is a version on the web somewhere. It is scandalous to give a presentation about ICT to an audience and force them into reproducing, in effect, a set of notes that you have already created! Besides, whilst they are taking notes, they are not actively listening to what you are saying.
Assume that people in the audience can read. I have never understood why some people read out each slide. If they need to, because people cannot read them, the slides have not been well-designed, or people have not been given a copy of the presentation to look at close up. The slides should be a starting point for more material, or a summary of something you have said. If all you're going to do is read out the slides, why not just give them a set of notes and head for the nearest café?