Hola! Pronto me voy de viaje a Colombia! 
So I wanted to prepare myself for the Spanish they’re using there… Which words, phrases, or expressions do Colombians use that might be helpful to know (in advance)?
I’m very much looking forward to learning more about Colombian Spanish! 
¡Quihubo Janina!
I will try to give you a list on some Colombian slang or just familiar language.
1. As you may already know our currency is the COP (Colombian Peso) and 1 Euro equals $3.877 today. 
So please be familiar with our bills and coins so you don’t get confused when paying. https://www.banrep.gov.co/es/billetes-y-monedas
The reason I mention this is because we refer to money as:
Lucas: usually written as lks. Most of the times this is less than $100.000
- Toca pagar 10 lks pa’ entrar al bar. (pa or pa’ is a shortened way to say para)
Barras: I have the impression it is used when the amount is more than $100.000 and less than $1.000.000.
- Necesito 500 barras pa’ completar la cuota del carro.
Palos: once you start talking about millions. But I guess you’re not spending palos on your holidays. 
- Tengo 30 palos pa la rumba de esta noche. 
(You will probably hear how that “de esta” turns into “desta” because of fast speaking.)
2. Greetings is such a long list. But In case you don’t know some of these…
Quihubo or Quiubo, that comes from Qué hubo.
¿Qué más?
Quihubo, ¿qué más? would equals Hola, ¿cómo estás?
Buenas
¿Entonces qué? / ¿Tons qué?
¿Todo bien o qué?
3. Be aware that many people (cashiers, clerkmen, etc, men and women) treat people with nice (sometimes too nice) words. I am pretty sure they will say to you something like:
- Buenos días, mona, ¿en qué le puedo ayudar? (mono/a is blond/e)
They also use words as: reina, reinita, corazón, mi amor, and any other cheesy thing you can think of. 
4. Many people call foreigners gringos. This is an interesting word to call people from the US (https://www.thoughtco.com/gringo-in-spanish-3080284). Anyway, when people are blond with light-colored eyes… they’re gringos. 
They may also tell you on the street: quihubo gringa.
5. In Colombia you don’t order things at a restaurant or at a store, you ask them to give them away. 
- Buenas, me regala por favor cuatro empanadas y dos Pony Malta.
6. There are so many phrases and words, así que te tiro un dato: en esos links hay muchas más cosas por descubrir. (Tirar un dato is to give an advice or a piece of information that might be useful.)
https://nataliajaramillomoreno.wordpress.com/jergas-y-modismos-colombianos/ https://www.youtube.com/watch?v=DP_bgKmbsek
P.D. In case you pass by Providencia: Cayo Cangrejo. 
Enjoy a lot! 
It is extremely important to know these words and sentences if you are traveling, at any time of the year, but mostly in December:
(Search for the words on Google images)
Me podría dar por favor un/una (and any word or combination of them):
When in Medellín:
When in Cali:
Have fun! I will try to come up with more things.
Thank you @Michi for the many different tips and expressions, especially the one about money was helpful. And I will definitely try to use “Me regala por favor …”. It’s always hard to be polite in a foreign language, so I’m happy I learned this expression from you.
@PauloA I’m getting veeeery hungry looking up all these words … 
¡Hola Janina!
So glad you are coming to the beautiful Colombia <3
Seguro la vas a pasar bien “bacano” 