The best way to understand this concept is through clear examples. For instance, restaurants often use warm colors such as orange, brown, and red inside their restaurants. Consumer research has shown that warm colors (especially RED) are able to to stimulate appetite. The color red also "instantly attracts attention and it makes people excited, energetic, and increases the heart rate." All of this occurs without you even consciously realizing it or controlling it. This is an excellent example of priming because you're "primed" and can find yourself feeling hungrier than usual and excited to eat something even if you didn't seem to have much of an appetite initially.
Consider another example. You are leaving a coffee shop, and on the way out, you see a group of smokers. As you pass by, the wind blows all their smoke in your face and you start coughing and get annoyed. Later on during the day, a person with a clipboard approaches you and asks you if you have time to sign an anti-smoking petition. Chances are, you're more likely to be open to the idea because of your previous experience during the day. The smoke being blown in your face primed you to be more open to the idea of signing that petition.
Now, let's tie this back to effective communication and influencing your audience. Let's imagine you are the head of the Bureau of Street Services department in a large city such as Los Angeles. You are a believer in native gardens and want to push the city to invest into creating such gardens at publicly owned sites. You believe that native gardens can be aesthetically pleasing while also providing benefits such as water savings and stormwater quality and quantity control. To effectively influence your audience, you should figure out a way of priming them before they even arrive to your presentation or meeting. Hold the meeting at a location that has beautiful native gardens along the path to the entrance of the building. Such a strategy will effectively prime your audience and it will also serve as a concrete and visual example. As discussed in previous posts, being concrete with your examples is quite effective. Seeing a real live example of what you are going to discuss is as concrete as it can possibly get.
Often times, effective priming will most likely be difficult or perhaps even expensive to set up but you should always keep the idea in the back of your mind and utilize it whenever it's realistically possible.