Is there any kind of generic guide for how to address different people? It can be different depending on the situation, your age, your position (within a company, for example). There are so many different names to call people it's hard to keep track...
Specifically, I'm 22 and I've been seeing this married couple (around 28-29) a couple times via church, and I can never remember what to call them. I feel awkward calling them 아줌마/아저시. Does 선생님 apply? What about just by name (with -씨)?