Hello, I'm new here and this is my first post. It is an interesting question, and one that I would like to know the answer to as well.
I guess sometimes you just know if a person is an ole' soul or a young'n. Kind of like intuition?
For instance, an old soul might have real good intentions and motivation, especially to help others, whereas a young soul may be self-centered and egotistic.
I think I have a long way to go and a few more lives to live, but at least I have the comfort in the knowledge that I have already started walking the physical path, and every experience (subjective or objective, good or bad) goes in the 'soul experience bank' which I can draw upon when I physically pip it!
Take it easy!