When you think you're done, use the index card method.

You’ve followed all my instructions, worked really hard, and finished creating your presentation.  So you think you are done, right?  Wrong!  Every time you give the presentation you will uncover ways to relate the same content with fewer words, fewer slides, and less overall detail.  You will become more aware of the essential and non essential material and find better words and visuals.  A slide presentation better and more concise with time and repetition.  Less will be more!  In the words of Mark Twain, "I didn't have time to write a short letter so I wrote a long one instead." 

One way to short circuit that “learning” process is to us the index card method when you first think your presentation is ready to go.  Write out a card for each slide and write (only) the takeaway message on each slide.  Try rehearsing the presentation with only the cards.  You can experiment with changing the order to see if that improves the flow of the narrative.  You may find that you can remove a card or two or maybe you need to change the takeaway message for some of the cards.