Are you a world citizen if not have you ever tried or else should I first ask if it is something acquired or congenital for you?
I do not support the idea of being cosmopolitan where it also means not being nationalist. From my standpoint, it just should work in the way of indigenizing the whole world as much as you do for your own nation.
Being a global citizen is not making any discrimination depends on people’s nation, language or religion. First things first whoever he is cannot change the fact that he is human in any way. Their behavior, leniency, kindness et cetera can be the only factor that you can categorize a person. His culture is not a criterion in the ideology of cosmopolitanism.
The next question is: How to be a world citizen? Some people believe having a command of more than one language will be sufficient. Unfortunately it is not the key but even so doubtlessly it will help too much.
You must travel, read, distinguish, develop your empathy sense because it is important to be open for every culture. Being open to new cultures does not mean growing away from your own culture moreover it is better to explore your heritage first. In the end, the closest ‘ideas, customs and social behaviors of a particular society’ is the one which you belong.
Get rid of your prejudice and be curious about others’ traditions. To make this happen you should visit countries and talk with local people about everything that comes to your mind. Of course, traveling and learning through experience is incomparable but reading cannot be disdained too. You can get whatever you search from books either. The world of books is endless and the time is too short. So read as much as you can! Having more than one language will help you incredibly at that point since it is hard to find either sources that are in your language or local people who speak your language.
Take an interest in local issues before global ones. Ultimately local problems exist in the base of global problems and without dealing with local difficulties you will not understand the global problems at all. It can just help you to be seen as “sophisticated”.
Lastly and most importantly put up a fight for injustice. No one deserves more than what other person has. We all live in the same world!