One of the most common mistakes is to start with a mountain of data and ask, "What can I cut?" Everything seems indispensable. As a result, scientists typically include far too many slides and rush presentations.

A more effective strategy is to identify the core message and "build up" from that message; adding detail in a manner consistent with audience knowledge and available speaking time. Add only detail that supports the core message. Start with a one minute version for a relatively unspecialized audience and ask, "What would I include if I had five minutes?" Repeat the process until you can fill the time that you have available.

The above slide shows this as building the presentation "up" from a single slide rather than "cutting" down from many slides.

More guidance on how to develop that core message in future tips.

You should probably use an outline slide in your presentation and return to the outline after each section of your talk.

I recommend creating a summary slide at the end of each section and before you return to the outline slide. This slide should recap the points the audience should have learned from the slides in that section.

You may ultimately choose not to use the section summary slides in your oral presentation. They may make the presentation too repetitive and pedantic. Still the process of making the summary slide will force you to consider whether the audience has learned what you want them to learn. Perhaps more importantly, it will force you to think though what you want the audience to learn!

The slides you include in your presentation should support an overall narrative or "story." As such, you should define your story prior to making slides. What is the problem? Why is it important? How am I approaching it? What results do I have so far? What have we learned? etc.

It is often difficult to articulate a narrative after months at the lab bench and many scientists begin the presentation process by creating slides. Slide making can get you thinking. That's OK, as long as you step back at some point and articulate your story in some type of narrative form. Otherwise you will end up with a largely meaningless collection of slides. The slides-narrative process can be iterative.

After defining the narrative, the process of slide making may lead you off in unanticipated (by the narrative) directions. Perhaps you remember some really exciting data that doesn't fit with the narrative. Fine, include it, but pull back and rewrite your narrative. A coherent narrative is the essential building block of a presentation.