Often times in American English, there is more than one way of saying something. For instance, when asking someone to pick something up at a store for you, you could ask any of the following: "Could you pick up some milk on your way home?", "Can you pick up some milk on your way home?", and "Would you pick up some milk on your way home?" In fact, all three of these mean essentially the same thing. I say "essentially" because some would tell you that "could" is more formal than "can" and if you look at it that way, then there is a nuance there; however, it is an insignificant one and any of these three are safe to use. The same applies to phrases used to say "hello" and "goodbye", to ask "How are you?", etc. Alternates exist. Let's look at some of them:
Asking How Someone Is:
Phrase books are going to give you the standard form "How are you?"; however, "How's your day going?" and "How's it going?" are two other phrases that you can use instead. In fact, "How's it going?" is a shortened form of "How's your day going?" as the pronoun "it" is standing in for the noun phrase "your day" which is assumed to be what you are talking about. Slang forms of both of these exist, of course, because you can replace "going" in both of them with "goin'"; that is, you can also say "How's it goin'?"
The slang forms "How's it hanging?" and "How's it hangin'?" exist too but I suggest you avoid them. First, these two forms make reference to a man's penis; that is, if his penis and balls hang low or comfortably, then things are going fine. Do you really want to speak to your boss like this? I wouldn't. It is so unprofessional. Furthermore, these two slang forms were used around the 90's by the younger crowd to try to seem cool. You hardly ever hear them now and Americans actually think these two phrases sound pretty lame when people say them. So if you've heard these two forms in American TV shows or movies, PLEASE remove them from your vocabulary or at least just don't say them unless you want people to think you are a loser. In that case, say them and repeat them over and over again. You will make a lot of friends. Yes, that was sarcasm. Hehehe. :)
Wishing Someone A Nice Day:
Again, the phrase books are going to give you the standard forms which are "Have a nice day." and "Have a good day.". In my part of the United States, I hear "Have a nice day." more often than I do "Have a good day." actually, but both will work. Again, another phrase exists though. For instance, you could also say "Have a good one." In this phrase, "a good one" stands for "a good day." This is my prefered form actually, and I hear more people say this than I do the others. Note that in my part of the English speaking world, "Have a nice one." is not a possibility though. You almost always encounter the form "Have a good one." at gas stations and stores. After you've paid for your merchandise, either you or the cashier typically says "Have a good one." and the other says "You too.". Then you walk away.
Yeah, that's my point. You can make money with your hobby. You would get lots of students here.
Anyhow, aside from that, I am always available to answer anyone's English questions so everyone should feel free to send me an email whenever they get stuck with English and I will try to answer and explain it as best I can. :)
Do you need to actually be certified to do that, as in have an actual degree in teaching? Not sure if they are trying to keep that reserved for actual professionals instead of people who don't do this for a profession, but instead just do it as a hobby. lol
Thank you. Why don't you teach here on italki?