People from different regions may use different ways to greet each other. I think 你好 may be the most common way to greet an acquaintance or a friend, but between close friends or family members, we don't use it. I think in the U.S, you don't greet your parents with hello as well. 您好 is only used in formal situation or greeting a person who's obviously older than you, sort of like "usted" in spanish. As for 你好吗, I've never heard any chinese people using that sentence to greet their friends. It's only a translation of "How are you", and we don't use it when we see our friends. So in conclusion, 你好 is the most common way to greet people, but once you became friends with them, you don't need to use these words, just say 嘿（hei）and smile will be enough.

你好, 你好吗？is really common and like you say it to your friends. it is quite an informal expression 您好 is usually to someone that you pay respect to, which is quite formal. other expressions like 好久不見 long time no see 很高興認識你／跟你見面 nice to meet you 請問... may i ask, please 早上好 good morning 午安 good afternoon 晚安 good evening

For me and my friends, we don't use 你好吗 for greeting. 你好 is the most common way to say hello when you firstly meet someone, it can be used both causlly and formally. 您好 is a more respectful and formal way to say 你好. For friends, you can just say Hi~ I think 吃了吗(have you eaten yet?) is not usually used amony young people. I have never say this as a greeting to my friends. But older Chinese always say this. And for friends that you haven't met or talked recently, I usually use 最近忙什么呢？(What are you busy with recently?) as greeting or the beginning of the conversation.

I think it is common to greet friends by using “你好”or hi,hello for elders who you are not very familiar,you can say 您好;otherwise,you can say 你吃了吗（it means do you have lunch/dinner） I think你好吗，usually be used when your friends are not happy.

hi~