Recently I re-signed for another year teaching in Suwon, South Korea. As such I had to make a visit to the Immigration Office to renew my visa. I was re-signing at the same school so I did not have to make a visa run to another country.
It was the first time I had had to do it as my school took care of this when I first arrived. Once you have been here awhile however they need to take your fingerprints which means you have to do it yourself.
The first thing I would advise is to make sure you have the right documentation, even if your school says its correct, check for yourself. Especially if you are having to make a long trip to your local Immigration Office, you don't want to get there and not have everything in order so have to come back another day.
The second thing is to arrive early, these offices see hundreds of people every day and the line gets big quick. For me it was not too big of a deal as the Suwon Immigration Office is not too far from my school. The first time I went was just after lunch and I soon realised that I would not be able to get seen that day. I had to be at work at 4 o'clock, I spoke with a girl who had a ticket in the 400 region and they were only up to about 200 and something. It turned out to be a good thing as my school had not checked with the Immigration Office and had not given me all the documentation that they should have.
All Immigration Offices are different so you really should check with the one that you are going to visit. Any time you need information about documents, visas or directions you should call the number 1345. Its the helpline and it has English (and other language) speaking operators that can help you out. I called them to check what I needed to take with me and they were very good.
At the very least you will need:
-Your Arc Card
-Your original job contract and a copy of it (You keep the original and they take the copy but they want to see both)
-Application Form (You get from the Office when you get there)
Your best bet is to go as early as you can, go straight to the ticket machine and get your ticket. That way you are already in line, after that you can get the application form and fill it in while you wait. You will also need to buy stamps (that's what the 30,000 won fee is for) there will be a counter selling these close by. I got there about 9:30 the second time I went and my ticket was already about 240 something. I had to wait about 4 or 5 hours to finally get to see someone.
Once you do get there if you have all your documents ready then its really quick. She checked everything was there, took my fingerprints on the digital reader they have there on the desk and then wrote a new date on the back of my ARC card. It took about 5 minutes, I was lucky that I was speaking to some other people during the epic wait and they clued me into buying the stamps - if you have not done that you have to run over and do it while they wait which would be pretty annoying.