1. older than you '네' close to your age '예' or '응' 2. if someone's name ends with final consonant for example, '영관' you should address '아' > '영관아' 3. actually, if you know cashier's name you should addree '씨' but in korea, most people call cashier '저기요'

I'm observing this question out of curiosity for a while and the 네/예 info was really worth the wait! oO Cool! But so that you don't have to wait longer for this detail: Yes, you were right about the vowel/consonant rule for 아/야. But since you seem to be using a full name down below there: I have only ever seen this with the given name only. Also, this is a banmal-only thing, of course. 씨 cannot be used all alone (unlike 형, 누나 and such), but it has to be added to something, just like 님, too. Usually it's used with a name. Please note that Koreans tend to use the given name here, too, unlike in the west. Especially when it comes to 님, instead of a name, often they use the name of the position the other one has. A bit like "Mr. President" / "Mr. Secretary" in English. This is a trickier thing because you're required to know the terms for several jobs if you want to do this. You only asked for real-life situations, but let me add this too, just in case, okay? Please note that you're expected to use formal styles on the internet, let's say in a place like this. Many learners tend to underestimate this rule, especially if they come from the West...^^ The usual way to talk to (and about) internet community members is <internet name>+님.

예 is typically used when someone tells you to do something. It's usually followed with 알겠습니다. You usually hear this from workers to customers but not typically to each other. Also when you are acknowledging something like if someone asked if that building is the 63 building then you would usually reply 예.<- this though can be used interchangeably with 네. 네 is usually with respect so I would just use that all the time with elders. 응 is the only one that's informal. 예 is not informal. so don't use 예 with friends. That would be weird.