Where is a good place to stay in South Korea?

The area should be good for retail and whole shopping. Also where can I go to get custom made clothing in South Korea?

Shop in Myeong Dong, Dongdaemun, and hit a Lottemart in the Sinchon area. If you are looking for some nightlife, stay out of Itaewon because it's not REAL Korea. Hook up with some friends and hit Gangnam, Apkgujeong, and Sinchon/Hongdae as well if you are a youngin. The best place in Seoul to stay would have to be the Sofitel Ambassador hotel in the central area. It's quite expensive however the service is outstanding and they now how to treat guests in the traditional ways of Korea. For custom clothing hit Itaewon like Marf said. But make sure you do some research on your size and how much a retail value of a suit like that might go. If you are new to Korea, some vendors hang out in the street and try to scam you with prices. Keep it within 150-200 bucks for a decent designed suit.

check out tongduchon

go to souel it is awesome there is great shopping in it, it is called Ieatwone (dont know if i speld it write) it is just out side of the army post youngsong. and in a five min cab ride u can go to a etronic mart. but in ieatwone u can get custome made suits for CHEAP and dresses. and a hour away there is a great shopting spot outside the airfroce base oshone. where they have a HUGE shopping senter and it is cheap i got a nice REAL leather jacket for only 100 dollars.
so go there

If you don't mind spending the money stay at the seoul Hilton.
It's right by Namdaemun shijang, and also close to Iteawon.
If you have Korean friends shop at Namdaemun, if not go to Iteawon, you can get custom made suits here for about 200 dollars. Takes two to three days though.

Seoul is the best place to shop.
When you go to Seoul, visit Myung-dong(氇呺彊) to shop.
I think Myung-dong is very fashionable and there's a lot to look around Myung-dong.
But if you prefer buying cheap but fashionable ones, go to Dong-dae-mun(霃欕寑氍? market.
If you go there, you can find plenty of clothes including custom made clothing which are really cheap.

seoul my man.