Good post over at HBR. I've certainly made errors in this regard.
Analyzing data requires a lot of work that no one other than the analyst should ever see. In order to get a handle on the data you might create many exploratory graphs and compute multiple statistics. After doing all that work, it's understandable that you want to show it to someone. But first ask yourself "why?".
Why use a particular graph? Why a particular computation? Presentation time is when you cut everything down to your essential message and conclusions. Showing extra stuff will just confuse your audience and obscure your message.
Imagine you're at a movie and after every scene they stop the plot to explain how they selected the camera angles and lighting. Then they show you all the footage they edited out and explain why they didn't need that footage in the final film. It wouldn't make any sense. The few people who care buy the DVD with the "director's extras". The rest of us just want to see the movie.
It's the same with data. Determine your message and present just that message as clearly and simply as possible.
Another HBR post covering the same issue.