Lifehacker writes about Take your PowerPoint slides Beyond Bullet Points where it says that Bullet points on a screen make information harder to understand, not easier.
In PowerPoint slide design – the basics Olivia Mitchell focuses on design tips for the Assertion-Evidence format. At the top of the slide is a simple sentence which expresses the message of the slide, the assertion. The rest of the slide supports that assertion. There are more tips in PowerPoint slide design – adding elegance and in The Top 7 PowerPoint slide designs.
PowerPoint Design in 2009: Six most recommended tips is a great post and I totally agree with this statement:
The slides should be simple, clear and easy to understand.
The third tip One idea per slide is a great one, it goes well with the Assertion-Evidence format mentioned above.