I have read extensively on the subject and the idea what I like best is that of Guy Kawasaki.

His proposal is 10/20/30 rule.

A PowerPoint presentation or similar:

* should have no more than 10 slides with 10 important ideas,
* should not last more than 20 minutes
* and should not have fonts under 30 points

Also suggests what should be the content of the presentation and their order (it is intended for submitting an investment project, but is easily adaptable to other projects):

1. The problem
2. Our solution
3. The business model
4. Base technology / magic solution
5. Marketing and Sales
6. Competition
7. The Team
8. Projections and milestones
9. Status and deadlines
10. Summary and Action Plan

Another site where you can see good presentation skills is Presentation Zen by Garr Reynolds.

Also interesting is the proposal César MartínOf elevation on how to make a presentation.

1. Learn well your stuff
2. Do not use PowerPoint, you must be the center of the display. Use your product demonstrations, images that serve to support your speech. What is not relevant to disappear.
3. Start with 3 key ideas, develops each and ends with these 3 key ideas again.