A global citizen does not really refer to someone who move around the world, live here and there, but a person who can help shape the world (or let's put it in smaller scale: the community), spread the ideas and bring a better living together with the neighborhood.
I believe there are some sort of qualities or mindset that set these global citizens apart from 'locals'. They are open-minded, willing to share their thoughts and skills, happy to make and adapt to changes, and probably explorers or travelers who have seen how people in other parts of the world live their lives.
I have been travelling quite a bit for some years. 80-85% of the time, I travel by myself. Being a lone traveler, I had much more time spent on talking to locals, sharing how I live in my place and how they live in theirs, plus simply wandering around. Then the more places I wandered around, the more I wondered.
Because of these wonders, I started learning the importance of respect to differences - be it cultural differences or individual differences. Frankly speaking, 'respect' doesn't mean I truly appreciate something or like the way it is. But these are the differences that won't kill others or harm others. It could mean a bit of tolerance at first, and some time or patience to understand why it happens, then either let it go or you share with the person (if he or she is happy to hear) what those mean to you from your 'different' perspective.
In fact, if you can respect others, you'll get the same level of respect from others. Eventually respect leads to peace.