I became a libertarian about the age of 12. It began by questioning my religious beliefs. I remember going over all the why's and what's but specifically "what gives me the right to ----?" Most of the time that blank was "preach my religion to others." Despite my religion saying god/leaders command you to, I came up with "I have no right."
Things started to fall in place from there. Who has the right to tell me to do this, to do that? Or even deeper, what is the intent and desired results that whatever is trying to achieve?