Bad presentation often gets in the way of good science. It's a shame, because science is awesome. I used to complain about bad presentations at conferences but I realized that (1) I hate complainers and (2) as a professional science communicator I should probably quit complaining and actually offer people some help with communicating better. If you're a scientist who's interested in improving how you present your science, read on.
If you don't have time to read, I can summarize my advice in three words:
Respect your audience.