This first way to finance your studies is through scholarships, which are generally divided into 2 types:
Merit-based scholarships are offered for outstanding achievements in academics or other areas such as sports or arts. They are highly competitive, and usually given to a few students per year. Some examples are Clark Merit Scholarships (US) and King’s College Scholarship (UK). In some cases, students are automatically considered for this scholarship, while in others, you are required to fill out an application. The amount of merit-based scholarships varies, but in the best cases, they can cover 100% of your expenses.
Need-based scholarship aka Financial aid
Need-based scholarships are offered based on a student's ability to pay for college. The amount of financial aid is determined by each family’s financial circumstances. In addition to the standard set of documents, you will be required to provide official documents, such as a bank statement and parents' salary, confirming your financial situation (in the US it's called CSS Profile). The bottom line: you will get the money if you actually need it and you get accepted.
Not every college meets 100% of demonstrated financial needs, you always need to double-check that on the university’s website! Keep in mind that you need money not only for tuition but also for housing, books, meals, and tickets. Some universities that cover 100% of your needs are Columbia University (US) or Harvard University (US).
The next type of scholarship is provided not by the university itself, but by the external sponsors, or even the government! A few examples are MEXT Scholarship (Japan), Stipendium Hungaricum (Hungary) and Lee & Won Foundation (Korea). Each scholarship has its own requirements, which you need to carefully check on the website. They are quite prestigious and highly competitive, but very generous!
My least favorite method that is not suitable for everyone: the sponsor covers your expenses, which you later have to pay with interest. The amount and interest rate will depend on the country and university, here is an example of a zero-interest loan from Weill Cornell Medicine - Qatar.
As an international student, it can be difficult to get a loan, especially in the US, so make sure to explore other options and have a serious conversation with your parents. In the US you would generally be asked to have a guarantor — a US resident or citizen who provides a guarantee of repayment.
These are scholarships designed to support a specific category of people, such as scholarships for women, scholarships for minorities, and scholarships for students with disabilities. The amount of money and conditions depend on each organization. I would recommend searching for these in Google using relevant keywords.
And finally, you can enter a university with free tuition, which is possible for international students! Free universities are most common in Europe: Germany, Czech Republic, Austria, France, Italy, Norway and Greece.
However, there is a catch! In many cases, you can study for free provided that you study in the language of the country where you are applying. But there are also programs in English! Keep in mind that you would also need to cover your living costs, which can be done with scholarships or on-campus jobs.