Once you fully understand your client, you can then change shoes, and put on those of your audience. Investigate the standard criteria, of course, but where you can, delve deep into their passions as well. Converse with a selection of them in person, if possible. Or consider online customer surveys if your audience is large, or extremely broad. But again, try to find out their wants, beliefs and needs by asking the right questions. Then, translate the responses into a message that is truly purposeful and that clearly resonates with them, and with your client. One way to do this is to match up those areas about which your client and their audience appear to feel most passionate, and there you have your key messages.