The worst way to prepare a presentation is to start by making slides. A presentation should be a coherent narrative. Slides inherently fracture this coherence into individual pieces (each slide). It is very easy to get caught up in the details of each slide and lose the coherence. Below are three techniques to avoid this problem.
1. The Essay
On the September 2, 2014 "tip," I suggested speakers write a one page essay identifying all the points they intend to cover in the talk. Prose are inherently more coherent than individual slides. This essay should be geared toward the least informed member of the target audience (not all members of the audience, but the least informed that you care about reaching). It should not contain data, but should be used to form the narrative. It should identify are the key points that will be "proved" in the slide presentation. It should have an introduction, methods, results, conclusions.
2. The "Chalk Talk"
A lot of biologists are not comfortable with writing an essay that doesn't include figures and schematics. If this is the case for you, I'd recommend you prepare a "Chalk Talk" before drawing slides. A "Chalk Talk" involves going to the chalk board (or poster board on an easel), giving a talk, and drawing figures as they are needed. Since you need to draw the figures in real time (don't draw them in advance) you will be forced to include only the essential details. Your oral narrative will be simple and straightforward and you will cover all the essential points. You can then begin to think about visuals that support that simple oral narrative
3. The "Index Card" Method
Method 3 should probably be done after (and in addition) to methods 1 and 2, but might do as a substitute.
Get some index cards and envision every card as a slide in your presentation. You may write one sentence on each card. That sentence should be the main message of the slide. After you've done all the slides (index cards) see if you can talk your way through the presentation using only the index cards. Just like in the essay, you don't need to talk about the actual data, but you do need to say (qualitatively) what the data will show. When you go to draw slides, include only material that helps you make the point labeled on the index card.
You may want to lay the index cards out on a table and move them around to find the optimal flow of information.
