Waygook in Korean means “foreign lands” or “foreign countries”. Even though waygook seems to be the local English slang word for foreigner, waygookin or waygook saram is how a Korean would say it. Konglish is annoying but Engookaw is just as bad.
Also, in a taxi, when you tell the driver where to go, all you have to say is the location + eeyo. The same goes for ordering food, although joo-say-yo is okay. When you order beer, make sure to use Korean (and not Chinese) numbers + byung, although gae also seems to be okay (maekjoo saybyung); say jang when you get a cup of coffee (ameleekano hanjangeeyo).
Try not to speak banmal to people. I don’t know how many times I’ve inwardly winced while listening to people I know unintentionally insult their Korean friends or waiters by speaking to them as Koreans would speak to small children or animals. Everything you say should probably be ending with a -yo sound, and when you refer to yourself you should say chayga or chonun. Referring to others is sometimes so complex that if you’re confused you just shouldn’t refer to them at all, although if you must it’s best to do so in the third person with their job title attached to the end. If you’re not sure what their title is, just call them shee, for Mister or Misses, i.e., Kim Jong Il Shee. If you don’t know the person’s name, calling them sonsaengneem (teacher!) seems to work pretty well in most circumstances. To get a waiter’s attention, say yogeeyo (here please!). Pay attention to the tones Koreans use to make your own Korean sound better, and practice conversation with a tutor to increase your confidence. Obviously.
There are also more polite ways you can use to ask your students to do things, such as (verb stem) + bo-say-yo (읽어 보세요, read this please); (verb stem) + myun+ an-day-yo (가면 안돼요, don’t go please) is a polite way of asking someone much younger than you not to do something, although (verb stem) + jee-ma-say-yo (하지마세요, don’t do that please) also works. Koreans would generally seem to be amused whenever foreigners speak banmal, children included; these will probably speak banmal to you, which they would never to do a Korean, if you speak banmal to them.
As for my credentials, I’ve been studying the language for three years, I live with a Korean woman who is also my wife, and try to speak with her (in Korean) as often as possible. I checked with her before posting this. I meet once a week with a tutor to practice conversation (where I’m able to discuss politics and other abstract subjects), am currently reading through this textbook, am working through Monnara Iootnara (ignorance and anti-semitism notwithstanding), occasionally attempt to read the news in Korean, and have very little trouble making myself understood in most circumstances, although when I just tried to get some ground (원두 or 간 or 분쇄) coffee I was completely at a loss and had to revert to English to explain myself. Then when the woman at the counter asked after my son, I accidentally told her that he was dead (이제 없어요), when in fact I just meant that he wasn’t around.