It has been a while since I entered POSTECH as a freshman back in 1997.  Admittedly, things have changed quite a bit over the years, and my personal experience is bound to be limited in scope.  Still, I am delighted to have a chance to share my experience on studying abroad after finishing my undergraduate degree at POSTECH. 
There are a number of factors that you need to think about if you are considering studying abroad. First, one of the major factors to consider is the excellence of programs and schools you would like to attend. One of the potential advantages of studying abroad is the chance to be exposed to cutting-edge academic programs, and that also includes the body of an excellent faculty and competent peer groups. Second, there are cultural aspects in choosing the location and country for studying abroad. There will be a number of differences not just in how you approach academic matters, but keep in mind that it will be helpful to learn about the cultural aspects as much as possible. Third, you will need to consider that there are a number of challenges as well as opportunities in living abroad. At the beginning, you will leave your social network of family and friends behind, and you will face various challenges as you navigate through your new environment mostly by yourself. 
Fortunately, for POSTECH students, there are a number of institutions that offer student exchange programs.  These can be great venues to have an early opportunity to explore the universities in different parts of the world. This typical one-semester long exchange program can provide you with opportunities and practical challenges firsthand, and it would help you weigh the pros and cons when you consider studying abroad. 
I had a great opportunity to attend an exchange program at the University of Maryland for the second semester of my junior year. However, upon consulting my undergraduate advisor and other professors in the department, I decided to focus on graduate school applications during that period rather than going for the exchange program. I was fortunate enough to start my graduate studies at the California Institute of Technology in the United States. The California Institute of Technology, also known as CALTECH, is a small school that focuses on science and engineering disciplines, and it was also a model for POSTECH. Indeed, CALTECH has a small student body of about 200 undergraduates admitted each year and a relatively large body of faculty members.  There are interesting science insignias throughout the campus like the Gene Pool and orbital-shaped lamps on campus. CALTECH emphasizes interdisciplinary work and promotes an undergraduate research program, SURF, which is a 10-week long program, a bit longer than a similar undergraduate research program in POSTECH.  Students are encouraged to take advantage of the small student body and closely-knit interdisciplinary programs where students can freely interact with renowned faculty members and start their own research projects as undergraduates and work throughout the academic year if time permits. 
As a first year graduate student, I initially met with the bright California sun, a heat wave beyond 100F and severe dryness during my orientation period. The faculty advisors for first year students were all nice, helpful and tried to be accommodating.  Still, it was challenging to express my thoughts clearly and sometimes there would be noticeable delays since I was trying to translate Korean to English in my head.  Things definitely got better as I spent more and more time with classmates and other friends, and I felt rather comfortable after about one year.  It would be helpful if you take the initiative to attend a number of academic and social events to get to know other people. The school and department would likely work to provide ample opportunities for new students to get acclimatized and it would be best to take advantage of these opportunities and support programs. 
As a first year graduate student, I was required to do quarterly rotations through different laboratories to explore different lab environments and advisors that could be good fits for each other. Fortunately, I had an opportunity to work with my thesis advisor who just started at CALTECH. My advisor finished his graduate studies at CALTECH, initially working on neural networks in computer science, but later switched topics to molecular computation mainly using DNA molecules. There were numerous bright ideas and great advice I received from my advisor. Probably, the important lessons are about learning how to approach science and how to work with other scientists and students. I would like to share a couple of examples. During my research presentation in the early days as a graduate student, I presented the results from a relevant research paper. My advisor asked me, “What were the evidence they presented? Are they credible?” to which I did not have a clear answer. Looking back, I was reading research papers more like reading textbooks.  My advisor would stress that we need to read everything critically and to not take those research findings as facts. Also, during those early days, he came and said to me “I heard that Asian students always say yes when they are asked to do something, but I don’t want you to do that.”  I indeed felt hard to say ‘no’ when I was asked to do something back then. On the other hand, an American student typically would not hesitate to say ‘no’ to the advisor. Definitely, these cultural differences matter and he took the care to advise the students considering these different backgrounds. Sometimes he would add, “You can say no,” when I hesitated to answer to make me feel more comfortable.  
When you are applying for graduate school, I would like to note that it is important to look for an advisor that aligns with your academic interests. You also need to consider a number of other things such as your style of work and communication to see whether you can find common ground with your future advisor. It would most likely take time and effort to reach that common understanding, but it doesn’t hurt to look around to find an advisor that could be a good fit. 
In the end, everyone’s experience will be unique and different in many ways.  Still, I would strongly recommend POSTECH students to take the opportunity to apply for exchange programs during your undergraduate period. These exchange programs would provide great opportunities to explore different environments, different cultures, and a diverse pool of people. More likely than not, you will be able to learn something valuable from the experience.