Start by taking a pen and paper. If you don't like paper, open up your favorite mind-map software.
The first step is to map out your client's business (or your own, if you're creating a copygrid for yourself).
Here's how I do it:
The benefits of mapping out your client's ideal customers:
You keep the focus of the conversation on where it should be.
Any seemingly off topic conversation can become a useful note about other parts of the clients business (less waste).
You make the client understand you're listening to him and taking into account all the customers he wants to be selling to. You do this not by telling him, but by showing him. You have a tool on the table that is constantly reminding him of this - making him relaxed, allowing him to know you have everything under control, and that you know what you're doing.
You help organize the client's thoughts - which makes him feel good, and helps you jump back and forth between different trains of thought (without breaking a sweat).
You have a visual cue that allows you to make sure you and your client are both on the same page.
In the video also talk about how I use multiple grids at the same time during meetings. You shouldn't have to worry about that to much for now, I'll discuss and explain this later when I show you the next steps of the work flow (and when you already understand how to use the grid).
When you're finished mapping out the business you currently want to work on, go to step 2.