Follow the steps that Marc Ensign outlines here: The Tale of Inspiration, Perspiration, Preparation and Celebration.
I am convinced that people who give a great presentation do it because they put this much into the presentation. For people who give so-so to good presentations, including myself, you likely just manage to get it done. For people who give great presentations, they do all the things that Marc outlines here.
If you are wondering is it worth it, I can say that it is. I have given a small number of really good presentations, and every time I have, they were good because I went through a process similar to Marc’s. What strikes me is that years later, I am still happy and proud to think of those talks that I gave. That’s what makes me think it’s worth doing all of the things that Marc talks about.
Needless to say, I highly recommend this advice and Marc’s piece. Bonus: he’s funny.