Annyonghaseyo(안녕하세요) ( ' ▽ ' )ノ : A formal greeting meaning "hello!"
Annyong(안녕) (・∀・ ): Informal way to say "hello." Typically used amongst close friends. If you are older you can say it to someone who is younger than you.
Yobeosayeo(여보세요) (°ロ°)☝: "Hello" when you pick up the phone.
Ajumma(아줌마) ( ̄(エ) ̄) : What you can call an older woman. Generally, the woman should be over 40 years of age as it can be offensive if they are younger.
Ajusshi(아저씨) ( ̄(エ) ̄): What you can call an older man, same rule applies as to ajumma.
Dongsaeng(동생) (◕ω◕✿): "Younger sibling." You can refer to your own younger siblings as dongsaeng or a younger person who is close to you.
Hyung(형)/Eonni(언니)ヽ(*・ω・)人(・ω・*)ノ: What you can call your older sibling (hyung=male, eonni=female), or someone older of the same sex that is close to you. Sometimes you will even hear tom-boys call her older guy friends hyung!
Oppa(오빠)/Noona(누나 ) (ノ◕ヮ◕)ノ*:・゚✧: What you call your older sibling of the opposite sex (Oppa=what girls call older guys, Noona=used by boys for older girls) or someone of the opposite sex that is close to you. Also used affectionately among couples!
Yeobo(여보) (。♥‿♥。): Used by a married couple, meaning "sweetie" or "honey"
Wae!!(왜) щ(ಥДಥщ): Why!!
Ottoke!!(어떻게!!) ((((゜д゜;)))): What to do!!
Jugulle?(죽을래?) ಠ_ಠ : Wanna die?
Yah!(야) (n'∀')η゚: Hey!
Neo micheoseo?(너 미쳐서) ლ(́◉◞౪◟◉‵ლ) : Are you crazy?
Michin nyun!(미친년!) ⊙‿⊙: Crazy bitch!
Shibal! (씨발!) (ノಠ益ಠ)ノ彡┻━┻ : Fuck, fucking
Kaja!(가자 ) (≧ω≦): Let's go!
Ggeojyeo (꺼져) ◡︿◡ : Get lost
Bbali!(빨리!) (┛◉Д◉)┛: Hurry!
Mianhae(미안헤) (╥_╥): I'm sorry...