While I appreciate Supermonkey's willingness to share his knowledge on how to have fun in Korea, I must point out that not all the information that he has been supplying is correct. I was born and raised in Seoul until I graduated from a college and I usually spend about 3-4 months per year in Korea. So I know the Korean entertainment scene inside and out. I am a management consultant, and my company gave me a corporate blackcard with generous monthly spending for entertaining clients, which is also helpful in studying the Korean entertainment industry
One of the incorrect pieces of information that SuperMonkey has shared in his early post: Tenpro does NOT mean the top 10% hottest girls. Instead, it refers to the payment system of the so-called Tenpro room salons (the arrangement between the owner of the salon and the girls; it is quite complicated so I won't explain it in detail). The girls working for Tenpro room salons are extremely pretty (many are much prettier than those you see on Korean soap operas, seriously). These girls usually do NOT go for the "2nd round"--i.e., going out with a client for sex. You can charm these girls if you have a lot of money or are very good-looking, but they won't have sex with you for a set price (e.g., $500, etc.). I dated one of these girls back in 2004-2005; although she didn't ask for money, it wasn't cheap (Hermes bag, Chanel watch, etc.). Going out with one of these girls is an investment proposition, which you want to avoid.
Tenpro is considered to be the highest quality (it will cost about S$2,000-3,000 just for a couple of hours of drink with the girls, no extra, other than chatting). The next level is "0.5". The quality of the girls in this type of bars are very high; often as good as Tenpro. 0.5 further branches out to "high 0.5" and "0.5". Apparently, high 0.5 is better than regular 0.5. Some girls in 0.5 will go out with a client for sex, and the price is somewhere between S$500-S$800. So I normally don't go to Tenpro (unless someone else is paying), but I usually go to high 0.5. If you want to go to a "high 0.5" place, you will need somewhere between S$900 (if you share the drink costs with 3-4 of your friends)-S$2,000 (if you go alone). The next levels are "Club," "Public," "Hardcore," etc. The hardcore places are getting more popular because it is...uh...hardcore and cheaper. Due to increased competition, the price for these places has been dropping. It usually costs about S$400-500 per person for a hardcore place. The service includes about 90 minutes of drinking at the bar (a private room) with a girl. You and the girl will go back to nature (you know what I mean), and she will provide you with some value-added services at the room. After that, you will have 50 minutes of fun time at a hotel room. A good deal. There are several good places.
The above are commonly referred to as "Room Salons" (private room bar). Then, there are bikini bars, room cafe, stand bar, etc. Also, there are many types of massage parlors (anma places), kiss room, daeddalbang (Masturbation places), Glass room, Telephone room, to name a few. Finally, night clubs are a good places to pick up regular girls (or working girls after hour). I will probably provide more information on these later.
Also, SuperMonkey's observation on foreigners is gravely incorrect. If you are a foreigner, you are at a serious disadvantage in Korea. Some (very few) Korean girls are drawn to foreigners, but most (95%++) won't pay attention to foreigners. Even those who are interested in foreigners will be interested only in Caucasians (Americans and Europeans minus Russian) and Japanese--basically from advanced economies. They tend to show severe discrimination against other Asian ethnic groups (other than Japanese). I feel very shamed to admit this because I am ethically a Korean. In fact, if you are a foreigner, you won't be admitted to many sex establishments (unless you are accompanied by a regular Korean customer). You have to be aware of this. This is same in Japan (unless you speak Japanese or with a Japanese, you won't be admitted to many sex establishments, especially high-end ones). This is bad, but this is also understandable in some ways. About 99% of clients of these places are Koreans. If there is a rumor that one place accepts foreigners, Korean clients will stop going to that place. So many places avoid foreign customers.
The places SuperMonkey referred to (e.g., Cheonyangri 588) represent the lowest quality sex establishments (brothels). These places are being closed down, and are desperate for customers. So they accept foreigners. But I don't really suggest you go there because the quality is horrible and the service is really bad (and the hygiene is questionable).
Apparently, SuperMonkey has been lucky in several occasions, but I suggest you do not generalize his luck. Korea is not an easy hunting ground unless you have a good guide. You are likely to end up at the low-tier market, and that's no fun. If you don't have a Korean friend, other places--Shenzhen or Hong Kong--will be better.
I have NO intention to flame SuperMonkey. He is a foreigner, so it is natural that he can have only limited perspectives. Thus I wanted to share the view of the majority.
Just my two cents.