Ohh, this is a good question.
I’ll start with your last question first, since the other one takes some more thought. 

Did you find that you had a lot of time after classes to explore Seoul?
During the weekdays, no. This was mainly my own fault for stacking classes from morning to night. Many people accommodated their schedules so that they could be done by noon and enjoy the rest of the day. I, on the other hand, had to be on campus from 9am till around 7pm, then I had to study, so there really wasn’t much time to go out after that. I mainly wanted units though, so it all depends on you. Taking a lighter course load with easy classes definitely allows you more freedom to explore, but stacking classes and taking a more difficult load like me is really no joke. You need to study at Yonsei. They place a really high value on education. 

What are your lists of do’s and don’t’s for Yonsei and life in Korea in general? 

Here are some bullets of things I believe to be important during your stay in Korea.

• Learn to read Hangul and speak at least a little. Seriously, so many people have asked me if it is possible to get by in Korea without knowing any Korean, and the answer is no. Every non Korean speaker ended up clinging to one Korean person/someone who could speak Korean during the duration of their stay in Korea, mainly because not many people in Korea speak English. True, the younger folk may know how to speak a little here and there, but you definitely cannot get around efficiently without knowing the language. The most important things to learn are with regards to directions, ordering food, and asking general questions. Don’t worry about conversational Korean for now. Just focus on leaning the basics of surviving.
  
  EXTRA TIP: If you act like a foreigner, you’ll get treated like one. This can be a good or bad thing. When it comes to being lost and asking for directions, people will openly try and help you, however, when it comes to shopping or taking a taxi, you will get scammed. This is another reason why knowing Korean is important. Taxis will try to charge you more, take long routes, and milk you of your money. Same with store owners. If you act like you don’t know what is going on, expect them to cut some corners to get extra cash out of you. Be strong, confident, and act like you know what you’re doing. 

• Don’t waste your time stalking “oppa” and living your life in Korea hoping that you will meet him. Honestly, more than half the people who study abroad in Korea come for kpop, and they miss out on the culture and truly experiencing life in the country. They’re blinded by going to music shows or concerts, camping in front of their entertainment company, and attending fan signs. Don’t be like that. You will seriously regret it. I understand that a lot of people will want to see a show or two during their stay in Korea, which is totally fine! But don’t let it get in the way of going out and doing everything else. There’s a world out there waiting to be explored. Don’t limit yourself to the hallyu wave.

• With regards to living on Yonsei, I recommend you exploring the entire campus fully during your first few days there. This way, you can learn all the short cuts to get to class. The dorms are REALLY far away from both classes, as well as the subway stations, so I really recommend getting to know the area during your first few days there to avoid unnecessarily long walks places. 

• Buy yourself a T-Money card; it’ll really save you. You put money onto this card, and you can use it to pay fairs for the subways and taxis. It really saves time. You can purchase these at and GS25 market. 

• On the subways and buses, do not sit in elderly or expecting mothers sections, even if the seats are empty. Stand instead, unless you want to get weird stares your entire ride, or even potentially confronted and yelled at. Also, keep your speaking volume to a minimum when in places like these for the same reasons. 

• Ladies, make sure to keep your cleavage and most your shoulders covered when going out. It’s considered inappropriate to do otherwise. On the other hand, wear as short of a skirt or shorts as you want. That’s completely okay, for some reason.

• When getting food, tipping after paying is considered rude. So don’t do it. Lucky for you! You get to keep your money.

• If you go out drinking with Korean friends and classmates, remember seniority. If they are above you, when you clank glasses, make sure yours is below theirs, then turn your face away before drinking.

• When in a situation when you must give or receive something, place on hand under your wrist or lower arm when doing the action. It is considered polite.  

• It is completely okay to get to know your teachers and go out to get dinner or coffee with them. You’d be surprised how close teachers and students can get outside of class. Of course, I’m not implying close in a romantic way, but the bond you could develop between student and teacher is really not something you can experience anywhere else. Talk to your teachers! Get to know them! You’d be surprised how cool they are!

• In Gangnam, if you are a girl, you may find yourself suddenly being grabbed by club promoters and dragged towards clubs. In the case that this happens, if you firmly shake your hand off of them and speak something random in English, they’ll usually get intimidated and let you go. Works like a charm. 

• If you ever find yourself in Garosugil, dress nice. You’ll definitely thank me for this later. You’ll feel out of the circle if you don’t dress accordingly and happen to make your way in the area. Everyone over there pays extra attention to fashion, and they all look like they are straight off the run way. 

• If you are looking to buy make up and face products from the beauty stores around Seoul, they all have huge sales at different times throughout the month. I’d wait to buy the stuff you want until I know there’s a sale going on. You can check when these sales are going on online. You’ll save a lot of money. 

• If you’re a foreign girl, you’ll get approached on a daily basis by random guys on the street wanting to take you out to dinner or random dates. I just suggest caution when determining if you want to actually arrange something or not with them. Bring a friend with you if you decide to actually go for the first time. Just be safe.
  
  
• However, don’t feel shy to approach someone if you want to get to know them! Go out of your comfort zone and strike up a conversation if you want to. You’d be surprised how many friends I made with locals this way. 

I hope this was enough to answer some of your questions. If there’s anything in specific you need, send another ask. I’m not sure if I covered the stuff you were looking for.