I took the express train from Incheon Airport to Seoul Station becos I need to deposit my luggage there before making my way out of Seoul. I will be staying in Hongdae when I am in Seoul. I chose to deposit my luggage at the Premium Pass Travel center in Seoul Station becos they open at 8am. The ones in Hongdae open later.
Information and pictures are easily available online eg Theseoulguide Indeed taking the express train was much more comfortable as you will be guaranteed with a seat. In addition, you need not faced the crowds unlike the all stop train especially after a 6 hours flight journey, I need a peaceful rest. I did not book the ticket in advance cos just in case there was some delay. I bought the ticket at Incheon Airport and showed them my Asiana boarding pass to enjoy a discount for the train ticket.
Just a side note, I bought my EG sim card from Changi Airport before my flight. The staff activated for me(just before the queue built up. Phew). I have always used EG sim card during my trip but this time, I couldn't have any access to data until maybe half a day later when I reached Korea. I experienced no data access twice for more than half a day. Eg Sim card was unable to give me an answer as well.
From Seoul Station, I took the subway to Yongsan Station to take KTX to Jeongeup Station. Oh! I still have not mention where I was heading to. I was heading to Jeongeup for Naejangsan ^^ My KTX train departed from Yongsan Station at 9.50am and reached Jeongeup Station at 11.24am.