You can say 안녕히 주무세요 to people much older than you, like your parents or your teachers. 잘 자요 is the most safe greeting. I mean, it will not be very impolite no matter who you say it to. 좋은 꿈 꾸세요. [Informal]　　　　　　좋은 꿈 꿔. [Between close friends] 잘 자, 내 꿈 꿔 ▶ Good night, dream about me. It's said between close same-sex friends(usually girls) or couples. If a guy is your close friend, you could say it a bit of fun. Remember 잘 자요 as a general night greeting ;)

> good night, sweet dream of me! 잘자~ 내꿈꿔! (jal-ja~ nea-kum-kuwar!) For woman and couples it could be funny~ lol but not recommend for guy to guy -_-

잘자 (between friends) etc..

안녕히 주무세요