I have just found my notes from a 1-day workshop with Edward Tufte that I attended in March. For my records, here are my takeaway points.
1 - Every meeting starts with a document. A 2 to 4 page handout, for shorter meetings. That includes lectures and classes.
2 - Study hall. After handing out the document, give people time to read. Don't expect people to read in advance - it is during the meeting that you have their attention.
3 - Flatness. It is easier to read data in a page than across several pages. Graphs and tables with more information are better. Spreading information over time in slides makes it unreadable.
4 - Whatever it takes. It doesn't matter how you produced the display, use what works.
Most important: don't hide your data and your documents behind Powerpoint. The audience can and will read the complete material. They don't need or want to wait for you to read it to them.