Nationalism will not work in the 21st Century.

You can't build walls that block out carbon dioxide, or that keep fish in your corner of the ocean, or that cut through the cords of the internet. You can't wall off an economy, you can't fully keep another country's planes, drones, or satellites from flying over yours. Nor can you block your homeland off from the troubles of the rest of the world -- Syria and Haiti do not exist in their own bubbles, terrorism pays no attention to national borders, and nuclear fallout listens to the winds, not to arbitrary, man-made boundaries.

The idea of being a global citizen is not a new one. In the 5th century BC, when someone asked the eccentric philosopher Diogenes of Sinope which country he came from, he said, "Kosmopolitês": "I am a citizen of the world." But while the idea of global citizenship -- which also goes by the names of cosmopolitanism, internationalism, mundialism, and a dozen more -- is not new, it has never been mandatory for our survival as a species.

It is now. But we're still learning how to do it right. Here's a basic primer for how to be a good global citizen.

1. Read

Read newspapers, especially international newspapers that leave behind the politics of your home country. Read The New York Times, The BBC, The Guardian, The Times of India, Al Jazeera, and The China Daily. Some -- or all -- of them will sound like propaganda to you. That's okay. It's good to read things you disagree with. You aren't just learning about what's happening in the rest of the world -- you're learning what other people think about what's happening in the rest of the world.

Read books on history, and allow yourself to read alternative histories. Read histories written by the victors, and read histories written by the losers. Read about what 1930's and '40's Germany was like in William Shirer's The Rise and Fall of the Third Reich. Read about what the poor of South America think of the United States in Eduardo Galeano's The Open Veins of Latin America. Read about the fights for economic, racial and social justice in Howard Zinn's A People's History of the United States.

Read fiction, especially fiction that is written by people who come from different cultures, different genders, and different classes than you. Read the short stories of Jorge Luis Borges, read the great Russian novelists, Tolstoy and Dostoevsky, read the Scots brogue of Irvine Welsh and the lyrical polemics of Arundhati Roy. Read beautiful books by people you would never want to be friends with. 

Every book or magazine or newspaper you pick up is a glimpse into another person's mind. You need to be able to empathize with people who you neither like nor agree with to live in such a diverse world.

2. Travel

Unlike reading, not everyone can travel. But you don't need to travel extensively to feel the benefits travel. Like reading books by people who aren't like you, travel gives you a glimpse into lives that are totally different than yours. And you don't need to go far to see lives that are different than yours. If you've lived in the suburbs all your life, go to the cities. If you've lived in the cities, go to the rural areas. 

And if you can, see another country, and try and stay there for a while. It's hugely important to just get out of your country's bubble. I was able to watch the 2008 election from Buenos Aires, and it was at once freeing to not have to be surrounded by the ugliness of the US campaign, and illuminating to watch the circus from the outside. 

3. Be humble

I spent a summer writing for an English language newspaper in China, and towards the end, I was complaining to an older British journalist about how Chinese journalists were cowards. He said he disagreed, and added, "I've found them quite brave." He told me how Chinese journalists can't be openly defiant to their government, and instead find subtler ways to undermine the state's propaganda. Like puns: when they were forced to report positively on an expensive, failed language-learning program, they called the students "cunning linguists." It was a tiny gesture of defiance, but it was a powerful one nonetheless. Not everyone can stand in front of a tank, but everyone can assert their dignity in tiny, subtle ways.

And it's worthwhile to learn to be suspicious of yourself when you think you know what's best for a group of people. As the late Terry Pratchett once said, "You can't go around building a better world for people. Only people can build a better world for people. Otherwise, it's just a cage."

You can do a lot to make the world a better place, but you will never fix everything. You can't control other people's lives, or think that you know what's best for them. Usually, people are pretty good at making decisions for themselves. Instead, you can learn how to respect other people's decisions, and then work with them to make the world a better place.

4. Learn how to give as effectively as possible

A more concrete step you can take is to make a regular habit of giving some of your wealth to others in need. But not all philanthropy is created equal: For example, after hurricanes, stricken areas are often flooded with donations of toys and clothes. These donations come from a place of kindness, but they are ultimately not as helpful as, say, providing clean drinking water, sending food aid, or funding emergency efforts would have been. Even though it doesn't feel as nice, donating money is usually a better way to give, as it allows people on the ground to allocate the resources as they are needed. Giving blood regularly is always a good thing to do, too.

It's also worthwhile to investigate the charities that you give to. Charity Navigator is a great tool for learning if a charity is corrupt or ineffective. Other search engines, like GiveWell and The Life You Can Save, judge charities based on the bang you get for your buck. They practice what is called "effective altruism," which basically asks: "How can I stretch my money to do the most good for the most people?" The charities they endorse have an outsized impact on the world around them, and make a very real difference in their world. 

5. Learn how to volunteer as effectively as possible

If you want to volunteer, it's best to ask yourself the following:

1. How am I best suited to help? You maybe shouldn't be building houses if you don't have a background in construction. Voluntourism, unfortunately, often does more harm than good. Instead, take a look at yourself: what are your talents? How can you be useful? If you have a special set of skills -- whether it's as a medical professional, an engineer, or in construction -- your help in countries that have a lack of people like you would be hugely appreciated. If you have more common skills, you can still do a lot of good -- but it might make more sense for you to stay at home.

2. Do I need to go abroad to do good? Do not make the common mistake of thinking that, because things are worse in other places, that you should go there rather than help at home. At home, you'll be helping in a culture that you know and understand, which will make you a more useful volunteer. Going elsewhere to do volunteer work does feel more exotic and "global," but we need all hands on deck everywhere. And if you can help at home, you should help at home.
3. How would I like to spend my time? We're really lucky to live in an age where websites like Volunteer Match and Idealist exist. Both of these sites are great places to start when you're looking for volunteer opportunities near you. You can also check out Moving Worlds, which can help you connect your skills to an organization that is in need of them.

6. Live your life intentionally

It's easy to live life on autopilot. Avoid that temptation: you can't change the world without changing yourself first. You can start by looking at ways to cut your carbon footprint. There are plenty of online calculators that will show you where you're using the most carbon. If you're a traveler, the Union of Concerned Scientists has a nifty little guide to the most carbon-efficient ways to travel. You can also invest in a bike (which is cheaper than a car anyway), or start taking public transport. 

If you don't want to support businesses that don't match your values, you can download Buycott, which allows you to enter causes you support, and then lets you scan a product's barcode to see if that company is against those causes. 

Intentional living is a small, but essential first step for becoming a full global citizen.

7. Take political action

You can bring your carbon footprint down to zero by riding your bike to work, by buying local, by using solar energy, and by eating sustainable food, but at the end of the day, there are another 7 billion people on the planet who might not be doing the same.

The only way to fix these major problems, a lot of the time, is through politics. A lot of people (understandably) hate politics, but it's not as hard to make a difference as you might think. Getting involved and organized on the local level can actually make a pretty huge difference in a pretty short period of time. And ultimately, it's the hundreds of little small changes that lead to the big change. You can join a local chapter of Amnesty International (if human rights is your thing), a local chapter of the Sierra Club (if the environment is your thing), or you could just get involved through your local church or preferred political party. 

Finally, if an issue matters to you, call or write to your local representative. You would be surprised at how helpful their staff is (assuming you are polite and civil with them). It is, after all, literally their job to listen to you and to keep your concerns in mind.

Being a responsible global citizen sounds daunting -- it's really not. It's simply a way of thinking. Instead of just thinking about what's best for you and people of your family, race, class, or country, you try and think about what's best for all people, and act accordingly. It's an exciting new world we live in -- and you get to be a part of it.

Matt is a writer and blogger who focuses on travel, culture, politics, and global citizenship. His hobbies include scotch consumption, profanity, and human rights activism. He lives in New Jersey with his wife and his Kindle. You can check out his work at the Matador Network, or over at his website.