Beatrice:
I do Seminar Presentations around the world, and have found that using only keywords on the PowerPoint slide makes for the most effective presentation.
If you have a photograph, clip art, or diagram which depicts the point you are making in your presentation, it's much better to use this than many words—and with only a short caption. Verbally tell your attendees what you need to communicate.
My entire presentation process, in fact, has moved to using PPT only as a backdrop for the presentation.
What you are sharing with the group to whom you are presenting is much more important than the PowerPoint presentation. It becomes even more important if you are able to use the power of the visual with the explanation of the concept through oral communication.
To drive home this process even further, share an anecdotal story with your group which illustrates the point in a context that they will understand. I find that if I'm speaking to IT groups, using IT language in a humorous way tends to lock them into the presentation. If I'm speaking to a medical group, I find an anecdotal story from medicine.
Generally speaking—and some experts in PowerPoints will argue this with me—the less written on the PowerPoint slide—and the less animation you put into the slide—the better. Keep the presentation focused on what you are saying, not flying words or spinning pictures, words that appear out of nowhere or visuals that appear as if by magic.
Simple, well-developed themes with anecdotal backdrops seem to hold the visual and audio "attention" of the audience the best. And do you know what is the most important? Have fun with what you are doing! It's absolutely contagious.
Hope that's helpful. Let me know if I can help you further.
Alan