The first step with working with an athlete or client is to understand what they want to accomplish, where they currently are in that process, and figuring out the best means of attaining that goal.
But what does that process look ?
Enter the "Needs Analysis".
This post by elitefts columnist Nic Bronkall is a great illustration of what you should understand about the goal of your client or athlete and how this information can help you make better training and programming decisions in the future.