It's exactly like using the DC metro system. It's only when you expect to the different that you will get lost.
First with every stop there's an opposite stop, I.e going in an opposite direction. This means that all bus route are eventually circles of a sort. So, if you get lost just stay on the same bus until it brings you back to point one. Unless that is you, armed with a map, are sure of your decoding skills (not to brag but I was...just saying.)
With trains they also go in circles as in back and forth. But I would recommend staying on one until it goes full circle. Unless, that is, you have lots of time to spare. This time I would recommend using both your decoding skills as well as your every bit of Korean. And if you focus all of your luck in one place you might encounter a Korean who know English and is willing to help you.
But let me explain the ridunkulous way that I got lost. First it will add to the ridunkulousness if I tell you that my homestay dad had explained to me that at every stop I should look for the one that is going in the direction that I want.
Lo and behold I find the location of line that I am supposed to take, mind you I haven't located the direction to take yet. So the minute I see a train stop on either side of me I enter. It gets worse. Instead of looking at the names of the stops, I count the number of stops till mine. So after a while I decide to look at names and none of the stations I am hearing on the intercom march up with what I am seeing (hold up almost got lost again cause I was typing instead of looking.)
Yo! I didn't. Made it there safe and sound but I feel bad that my friend had to wait at the station that long.