To begin the practice of self-inquiry, sit for meditation as usual. If you don't already have a regular practice, just sit quietly and allow the mind to settle naturally. Don't attempt to focus your mind or manipulate your experience, just rest as awareness itself. After 10 or 15 minutes, when the mind is relatively open and present, introduce the question "Who am I?" The point of this question is not to engage the mind, because the mind inevitably gnaws on questions endlessly like a dog on a bone, with little nutritional benefit. Instead, drop the question into the stillness of your being like a pebble into a still forest pool. Let it send ripples through your meditation, but don't attempt to figure it out!
When the pond is tranquil again, drop in another pebble and see what happens. Set aside any conceptual answers, such as "I am a child of God" or "I am consciousness" or "I am a spiritual being of light," and come back to the question. Though true at a certain level, these answers will not satisfy your hunger for spiritual sustenance. As you continue your self-inquiry, you may notice that the question begins to permeate your consciousness—you may find yourself asking it not only during meditation but at unexpected times throughout the day.