Regardless of the audience you are reaching with your poster, it needs to equally convey information while at the same time aesthetically appeal to your target audience. Some key points to remember are: 1) find a focus, 2) be consistent with details and 3) choose references carefully.
Simplicity rules when it comes to this form of ad layout in that if you have an ad that is too cluttered, the key points will be unnoticed. It is also important to keep it simple by only focusing on one key objective, staying away from fancy fonts, using big, legible fonts, nice photography and imagery and contrasting colors. I work with each individual client to ensure that all these key points are maintained visually and that each design is custom and focused on the target audience.