I don't know if it's the only practical one, but self-observation is definitely interesting. Personally, I haven't dived (yet) into the wisdom of, say, Gurdjieff and those lines of teaching. I came across the wisdom of Ramana Maharshi who, in my opinion, has a fantastic knowledge of the Self. You can search the Internet for his works such as "Who am I?" or "Self-examination". I personally observe the "Self" through meditation or through relationships with others. For example, I love to go somewhere in the forest/nature near the river, let's say and then go for a walk. For me, it is an extremely relaxing and peaceful activity in which, when I am in it, I perceive that I am in an altered state of consciousness. Thoughts are minimal, the inner feeling is peace and I just look at the wood, grass, river, listen to the sounds of nature and the like. If you don't do it yet, then you don't know what you're missing. ;)
Ian