I think it is safe to say that each of us, and if you have not you will soon, has had that awkward moment of walking around campus, seeing someone you know, and not knowing the social etiquette of how to acknowledge them. Here is a list of the different ways you can respond to this situation.
1. The Smile
This is the best bet when the person you see is nothing but an acquaintance or someone you vaguely know but still want to seem polite towards them. Always go for this approach when you aren't sure if the other person sees you as well. Out of all your responses this is the least incriminating, you could simply be smiling at anyone!
2. The Nod
Similar to the smile, this is for someone whom you want to know you are acknowledging them, but do not really feel a need to talk to them or actually do anything besides acknowledge their presence. The only exception to that rule is for guys. Nodding is much more common between two guys even if they know one another well.
3. The Half Wave
This may be hard to name, but we all know what it is. This is the simple raising of the arm about half way. Due to its easiness and simplicity, this reaction is best for friends from class who you sometimes talk to or for people you live with but do not hang out with very much. Pretty much do the half wave if you know the person well enough to talk to if you are randomly in line but honestly don't really think you could hang out with them for long periods or have not talked to them in a while.
4. The Hey
Deciding whether or not to say hey to someone may be the hardest decision on this list. On paper it may not be that hard of a decision, but the problem is that a hey can mean so many different things. It can be a whats up hey, an acknowledgement hey, a flirty hey, a don't talk to me hey, etc. Due to its ambiguous nature, the best advice I can give about saying hi to someone is that you only say hi if you do not mind having a conversation with them. You do not have to have time to talk to them in the moment, but in general you are okay, and maybe even like, having a conversation with them. A hi, what's up, hello, etc are okay instead of a hey as well.
5. The Hug, High-5, ect
Physically greeting a person with a hug or high-5, or whatever you do, is only acceptable if this person is a legitimate friend. This type of greeting is saved for those of your inner circle and therefore no more explanation is needed.
