If we think about Pareto's Law in communication skills, the 80% is covered by two really crucial concerns: narratives; and adapting to an audience. Let's take the second one first.
Understanding your audience
The starting point for any communication is to understand what your target audience will actually get from what you're saying. The classic mistake here is to go into a lot of technical detail with a non-technical audience, but we can go a lot further than that.
For any meeting where you're speaking, think about who is there and what their jobs are. Get to know people and learn about what interests them.
Communicating in narratives
Terry Pratchett once said that our species should be called "Pan Narrens" - the storytelling ape. We think in terms of narratives, with start, middle and end. Our narratives can survive for thousands of years by retelling, and a memorable narrative needs structure.
Knowing that, we can structure our own communications with narrative form. Start by setting the scene and providing context. Then go on to talk about whatever is your topic. Finally, leave your audience with a conclusion (they won't remember more than 3 points normally, so try to keep your conclusion pithy).
Keep those two rules in mind - "what story am I telling?" and "what is my audience interested in?" and your message will land well and be remembered.
