hmm well... you guys know that hello is anyeonoghaseyo (anyeong for short/informal)
and then there are a few different goodbyes. the easiest (and informal) one is also anyeong.
um if you're saying goodbye to someone who is staying at the place and you're leaving you say: anyeonghi kehseyo
and then if that person is leaving you say: anyeonghi kaseyo
anyeonghaseyo is technically "how are you" (literally: are you in peace?) but you wouldnt really respond to it as good or bad b/c it's a greeting.
to say how are you you have to say: otoke chineseyo?
the answer:
good- jal chineyo
busy: chohm bappayo
okay: kwenchanayo
to ask what are you doing you'd say: mweo haseyo?
and yeah =D