A phenomenal program and place to go if you want to improve your social confidence, be less of a picky eater, try new styles and clothes, explore nightlife, and learn meaningful life lessons.
So much of making the most of your time lies in preparation. Pack properly. Don't bring a lot, you'll want to buy a lot there. Don't bring overly colorful clothes (You'll stand out a lot!). Account for mid/post-semester travel when booking flights. Flights to Japan, Taiwan, and more are very cheap compared to from the states.
Be involved in KUBA! Go to the cheering orientations, the dinners, and more. They're more expensive than a meal on your own, but they are amazing opportunities to make friends with both Koreans and exchange students from around the world. I regret not going to my group's MT (bonding event) despite its steep price.
If you did this all over again, what's one thing you would change?
I wouldn't have limited myself by staying within a friend group at the start. Making the most of social opportunities like KUBA and befriending as many of your fellow TEAN students as possible is the way to go. You'd be shocked how much drama can occur despite only being a 4 month semester, so be cool and be friends with everyone, it took time but by the end of the semester I was the happiest I've ever been.