My standard response to this is the same one Chris Elliott used in “There’s Something About Mary.” I just cheerfully respond, “Each day is better than the next!”
No one ever calls me on it.
Yes and yes. I was trying to figure out how to say this before. But basically, no one expects you to be super upbeat and cheerful all the time. BUT not everyone needs or wants to hear your complaints, either. Time them judiciously and tell people who care - it’s actually better for you, than just to vent to anyone who will just be bored.
You can absolutely say your day is not going so good, thus launching into further conversation. This is Ok at the office. This is not OK at the checkout line.
Yeah my standard catchphrase is “Hanging in there, you?” That doesn’t mean I can’t find the convention irritating.
For instance, I know a guy who always says, “What’s up?” and when I answer back, “Not much, you?” he never says anything back. I would like to drop-kick his head into Lake Michigan.
“Oh I’m okay. But the day is young.”
“Meh. You?”
“Okilodokily!”
Don’t you by now know who that handful are? Why not just greet them with a “Good Morning” or “Hi!” instead? And only express interest in how they are when you really want to know? (Which likely is never.)
It’s a social nicety not really a request for information. Usually I say, “well, and you?” Depending on who it is, I might say, “Can’t complain - no one will listen!”
I became rather wary of asking people how they are many years ago when a neighbour took the greeting as an invitation to earbash me for up to 20 minutes about her every ache, pain and complaint.
I’m reminded of this exchange from Pulp Fiction:
Butch: “You okay?”
Marsellus: “Naw man. I’m pretty fuckin’ far from okay!”
We don’t work in the same place, do we?
I long ago figured out who not to ask - I’ll just say, “Good morning!” to those people. That doesn’t stop them from bitching about their lives to me, though. The worst complainers in the place can get pretty tricky. Now that I don’t ask how they are as a greeting, they’ll ask me how I am first, and because my mother brought me up right, my instinct is to reply, “Fine, and you?” BIG mistake.
I usually just snarl at people who ask that…
I hate this question, but I don’t answer it in a negative way, I’ll usually simply sidestep the question and say something to the effect of “…and how are you”? Or something like that.
If it’s a fairly close friend or acquaintance I’ll generally use a friendly slang saying like “fair to middlin” or some other silliness.
Easy solution to this first world problem. Just say “hi” and keep it moving.
having worked in nursing homes and gotten the Real Story more than once, I only ask “how are you” in any way if I have time to listen to their answer. because they might say “fine, how are you” but they might want to tell me a lot of other stuff.
to this day, I mostly say something else. Hi, or Hello! - that works. when people say “how are you” to me in greeting, I saw “hi” back. seems to work.
I generally say “Hey there!”
I may be mistaken, but I don’t think “How do you do?” was ever a working class convention.
I can’t understand why you like “how do you do?” and dislike “how are you?” when they are asking the same damn thing! WTF?
And variations of this question* have been used as a greeting (not a true inquiry requiring an answer) since the 18th century; some of you are a bit slow on the uptake, eh? 
- how do you do, how are you, how’s it going, how’s life treating you, what’s up, how’s it hanging, 'sup, whatcha been up to…
There’s a scene in Bonfire of the Vanities, set in New York, where the main character introduces his old-line WASP neighbor to his downtown criminal lawyer. The neighbor says, “How d’j’do?” and the lawyer responds, “Howaya?”
At work, in a bad situation, I’d just answer “Surviving!” and keep walking. It got the message across that I was too busy to stop, but not in a good enough place to lie and say everything was fine.
I knew a guy who answered “all the better for seeing you!”. It was charming the first time, till you saw him use it on everyone he met. Or at least every female someone he met
“Condolences” - you can’t go wrong with that.
I often wonder how rude my standard response is:
Some guy: Hey how ya doing?
Me: I’m doing good.
The point is, I don’t return the “How are you doing” bit. My justification for this is I’m a fast walker. If I’m passing some one in the hallway, I’m already going to be way past them by the time I blurt out “How you doing?” And then what? Am I supposed to slow down to wait for a response?
Screw that! 
Personally, I just like to do the polite head nod as I’m passing people in the hallway.
People at work ahve stopped greeting me with “How are you?” or “How’s it going?” since my standard response has always been “Not too bad, so far. But it’s still early.”
(This is better than the “It is a good day to die” I was using in college after watching Little Big Man too many times.)
In response to the OP, I’m probably a complainer, or an over-sharer. But I blame the person asking - generally if I answer “oh, fine thanks!”, they smile and look at me expectantly. Even if I ask how they are, and they answer fine, they still wait for me to volunteer the next snippet of conversation.
Which given my caffeine over-consumption, is generally a rant or a moan about something or other 
Maybe I just have a reputation as a gossip though, so they’re waiting to see what I come out with this time!
My standard response is “I haven’t killed myself yet today, so I suppose I’m OK”. I just hate it when people ask empty questions, which they can’t be bothered to understand the literal meaning of.