There are numerous international study programs at both high schools and colleges around the world. Some programs last two weeks, others are for a whole school year. While some are summer programs, others are semester-long. If there is an option at your school to host a foreign student, why not volunteer?
Give a foreign student the chance to see what it is like to live in your home! If you are a parent, show them how you do things in your family: what traditions are upheld, what a family dinner looks like, what you do on the weekend for fun, etc. Or if you are a student as well, show the foreign student around your school. Attending a new school can be overwhelming for everyone, much less if the school isn't taught in your first language or home country. Offer to help the student adjust to the class schedule and volunteer to show them after-school activities, too.
You will learn a lot about the visiting student's culture, and you will likely also learn more about your own! You will find many differences but also, surprisingly, many similarities between your cultures. Hosting a foreign student will make you much more aware of how big, and also how small, the world really is.
Offer to host a student for a year-long program. Truly adopt them into your family, and embrace them as one of your own children or siblings. If their family would like to visit, offer to host them, too.
If you aren't able to have someone live in your home with you, look into the various groups and clubs at your high school or college. There will likely be an international club, so get involved! Learn more about your fellow students and where they are from. Offer to show them around campus or town and help them navigate public transportation.
Learn how to become a host family.