Presentation Basics 4

The longer your presentation, the more variety it will need to create 'spikes' of interest or spikes of change. Such spikes might be:
voice: softer/louder/faster/slower
different medium e.g. the white-board
change of style e.g. from bullets to anecdote
interaction e.g. Q&A
a prop e.g. bring along a sample
etc.

Build in some spikes. Or beware PowerPoint Induced Trance or PIT.