During my recent trip to Seoul (end Dec 2015), they seem to have changed the rules a bit to make things easier for tourist to get their Tax Refund. I hope to give you a run down on what has changed here. My experience is at Incheon Airport so I am not sure if the other airports are the same.
I learned most of the Tax Refund procedures from reading this blog -
https://beautifulbuns.wordpress.com/2014/06...efund-in-korea/
I suggest you read this blog first as it offers a much better step by step explanation than what I can offer.
Two things have changed -

1. You do not need to show your items or get the Custom Officer to stamp your receipts if your total Tax Refund is less than KRW50,000 (per person)

2. You no longer need to line up at different Tax Refund agent counters to get your money. All
can be done at the same Tax Refund Counter found at Gate 28 (Incheon Airport) (see pics. 2 and 3)
With the new rules in mind, these are the following steps you want to take -

1. Most chain stores can issue you a Tax Refund receipt if your purchase is more than KRW30,000 on a single receipt but you got to request for it. So consolidate your purchases to meet this requirement. Tell the cashier you want a Tax Refund. They will print out the regular store receipt and also the Tax Refund receipt.

2. DO NOT filled out your particulars on the Tax Refund receipts for now. Each receipt is printed with the tax refund amount you can get back. You want to total them up maybe the day before your departure.

3. Once you know the amount you’ll be getting back, you can start filling out your particulars. Remember if your tax refund is more than KRW50,000 (per individual), you will need to see the Custom Officer, show your items and get the Tax Refund receipts stamped. If this is the case, you might want to split them receipts with your travel companions so that you can skip this step.

4. At the Airport, you can check-in your luggage as usual if your total refund is less than KRW50,000 since you no longer need to show your items.

5. If its more than KRW50,000 tell the airline staff that you have tax free items in your check-in luggage. They will return the bag to you.

6. After getting your Boarding Pass, drag yourself and your luggage (if more than 50k) to the Self Tax Refund machines. Look for a Burger King. On the right of the Burger King is the Oversize Baggage Check-in and right beside that is where the Customs Officer counter is. Then look further to the right (outer side) you will see some people lining up to use the Self Tax Refund machines. (see pic.1) Make sure not to line up at the wrong place as right beside that is another long line of people queuing up to enter the Security Checkpoints

7. At the machines, there will be some staff helping everyone. I’ve got no idea how to work the machine but the staff there will do everything for you. You need to give the Tax Refund receipts and passport to the helper and they will scan everything and the machine will print out another receipt. Once done, all will be return to you and you can now proceed to the Security Checkpoint and Immigration

8.  Those who have more than KRW50,000  Tax Refund must now go back to see the Custom Officer and get them to stamp your receipt and also show your purchased items if they want to inspect it. Once that is done, you can check in your baggage at the Oversize Baggage counter just next to it. After that you can proceed to the Security Checkpoint (which has a very long queue most of the time)

9. After Immigration, head to Gate 28 (see pic.2 and 3). If you pass the Louis Vuitton boutique, you went too far. Give the pile of receipts to the staff manning the tall tables. They will sort it out and ask you to line up at one of the counters to get your refund. You get your money back in a few currency of your choice. No MYR of course. I got mine back in KRW as it wasnt much, just KRW22,000. (see pic. 4)

10.  Now if you got back some money and want to buy some Duty Free stuff, I suggest you do so here after the tax refund. Once you take the train over to your gate, there are not many shops over at the other side.

Actually the whole procedure is fairly simple. Only my explanation makes it sound complicated.
One more thing, I didnt get back my store receipts as everything was handed to the Tax Refund Counter. If you need them, I suggest you take pictures of them.

You can also claim your tax refund outside of the airport but I do not know how. The locations are listed here -
http://english.visitkorea.or.kr/enu/SH/SH_EN_7_1_4.jsp

Pic.1


Pic. 2 & 3


Pic.4