Science communication is, in a way, an indirect way of communicating. There is not a lot of feedback from the audience to you. When preparing a talk, lecture, or article, think about your audience. Who are they? What do they know? What do they care for?
A sure way to engage your audience is to captivate them. Make them laugh, make them cry, make them think! Use their imagination to provoke a reaction. If you have the time, ask them something or let them do something. Your audience is already listing for an hour and will have to remain there for quite a while longer. Keep them entertained!
One tip is to make use of a 3D object to show during your presentation. Do you study the bacterial community at the roots of strawberry plants? Bring a plant and show them the roots, as one of my competitors has done. If I see you doing something, I can imagine doing it myself.
'Storytelling is the most powerful way to put ideas into the world today' ~ Robert McKee
Scientists like to talk about facts, journalists want to tell a story. Facts push information out and are about knowledge. A story draws people in and is about remembering and understanding.
When you convey your research, try to structure your talk as a story. This can be your story, how you struggled in the lab to get to your results. It can also be the story of the objects of your research: tell the tale of the bacteria in your gut, how they struggle to survive and how they will rebel to you if you keep them unhappy by eating junk food.
My research is about developing machine learning methods to learn from pairwise data - about as far from a story as you can imagine. To explain my research, I told the tale of a zookeeper who received a new animal and did not know what to feed it.
In addition to your content, you will use your voice and body. One of my first experiences as a teaching assistant was teaching for seven hours straight. This has taught me the importance of using your voice correctly if you want to last the day!
It is in our Flemish culture to enjoy a smooth and soothing radio voice. A pleasantly sounding voice that will last through the day comes from breath from the gut. To force this, our voice coach recommended us to pinch our buttocks tight when presenting, so we are inclined to use our stomach to breath. I don't know anybody who actually does this though...
Whether you just give a presentation or if you teach a lot, the correct use of your voice is essential. Several exercises can be done to train your vocal cords. My favorite practice is to improve articulation. Put a small cork in your mouth to keep your jaws open and do your best to read some longer words as clearly as possible. Immediate results guaranteed!
When presenting, I dislike movement as this is distracting noise. I try to have a stable position, with my feet more or less directly below my shoulders. Hands are essential to accentuate what you are saying. Practice some movements to help you explain things. Remember, you are not a T-Rex! No need to keep your elbows fixed against your body!
The most important lesson of all: be yourself, it is your story! It does not matter that you have a raspy voice or that your research has no direct application. I want to hear why your research matters to you.
I consider myself to be a shy and introvert guy who has to push himself every time to stand before an audience or class. Still, I try to subject myself to giving presentations, lectures, tweeting, and writing because I love to talk about what I do. The most fun part of my job is working together with students and colleagues, doing the science thing and making and investigating stuff. Finding people to work with is only possible if many people understand what I do and want to get involved. That is why science communication is important to me.