Subway stations get very crowded but, thankfully, there are a lot of signs in Korean and English that have helped me navigate. It's common for bus drivers to speed off before you can get off the bus, so the phrase to remember is naeril-keyo, which means "I'm getting off." It's a good way to let the bus driver know that you need them to open the door so you can get off before they drive away.
In South Korea, there's something called the ppali ppali culture which means that people are always in a rush. People on the sidewalk walk quickly and will push past if you're in the way. They don't mean to be rude, they're just trying to get to the bus on time. I've seen people run for the bus and the subway. I've even done it myself!
