While the SOP breaks down the process of drafting this profile down into simple steps, I want to stress that this particular Quest is the MOST IMPORTANT THING YOU CAN DO IN YOUR BUSINESS. We're not here to serve ourselves, we're here to serve our customers. The best way to serve your customers is to know them as deeply as you possibly can. A solid product says "I hear you, I know you, I understand you, and I made this for you" to the customer.
Get your ideal customer nailed down, and everything else in your business will follow suit (for the most part).