Hello! (This formal greeting is used towards strangers and elders)

Anytime you want something, whether it be food or an item say, “Juseyo.” Which means, "Please give it to me." Place your desired noun before “juseyo.”

떡볶이 주세요.
Tteokbokki juseyo.
Please give me spicy rice cakes.

김밥 주세요.
Kimbap juseyo.
Please give me kimbap.

계란빵 주세요.
Gyeranbbang juseyo.
Please give me egg bread.

순대 주세요.
Sundae juseyo.
Please give me blood sausage.

붕어빵 주세요.
Boongeobbang juseyo.
Please give me carp-shaped pastry.

Let’s say you want ONE of something. Like ONE sweet Korean pancake. Then you’d say:

호떡 하나 주세요.
Hotteok hana juseyo.
Please give me one hotteok.

But what if you want two?

호떡 두개 주세요.
Hotteok doogae juseyo.
Please give me two hotteok.

If you don’t know the name of the food, then simplify your phrase by taking out the noun.

하나 주세요.
Hana juseyo.
Please give me one.

If you want two, three, four or more of an item, fill in the blank. Use the Native Korean number system, not the Sino-Korean Number System.

_____개 주세요.
_____gae juseyo.
Please give me _____ (pieces/units).

두개 주세요.
Doogae juseyo.
Please give me two.

세개 주세요.
Segae juseyo.
Please give me three.

네개 주세요.
Negae juseyo.
Please give me four.

다섯개 주세요.
Daseotgae juseyo.
Please give me five.

여섯개 주세요.
Yeoseotgae juseyo.
Please give me six.

If you don’t know the name of the item you want, point at the item and say:

이거 주세요.
Eguh juseyo.
Please give me this.

But maybe the item is a bit far from you. Then say:

저거 주세요.
Juhguh juseyo.
Please give me that.

Sometimes you pay a set price per item. Other times you give them a price first. This situation can occur when you buy sweet potatoes and chestnuts. 

5,000원 어치 주세요.
5,000 won eochi juseyo.
Please give me 5,000 won worth of it.

As the vendor prepares your food, you get your cash ready.

How much is it?

The vendor hands you the food. Be polite and say:

Thank you.

You have a bite of your amazing food. Woah, it is delicious. Let the vendor know.

맛있어요. 진짜 맛있어요.
Mashisseoyo. jinjja mashisseoyo.
It’s delicious. Really delicious.

As you leave, greet them goodbye with a slight bow.

안녕히 계세요.
Annyeonghee gaeseyo.
Goodbye. (Use if you are leaving and the other person is staying where they are.)

A couple hours later, you’re dreaming about that crispy boongeohbbang. You want more. Or maybe you wanna get some for your friend. Whatever the case, when you go back to the stall, you say with a smile:

또 왔습니다!
Ddo wasseubnida!
I’m back!

Here's a list of some popular Korean street foods:
순대 / soondae / blood sausage
떡볶이 / tteokbokki / spice cakes
붕어빵 / bungeoppang / carp-shaped pastry
김밥 / kimbap / Korean rolls
닭꼬치 / dalkggochi / chicken skewers
번데기 / beondegi / silkworm larvae
뽑기 / ppopgi / old-fashioned sugar candy
꿀타래 / kkultarae / dragon’s beard candy
계란빵 / gyeranbbang / egg bread
어묵 / eomuk / fishcake
고구마 / goguma / sweet potato
호떡 / hotteok / sweet Korean pancake