I usually tell them the truth. This tends to break them of the habit of using “How ya Doin’?” as a substitute for “Hello.” It also guarantees that I’ll be left alone, which is what I usually want anyway.
It’s a long way to heaven, but only three short steps to hell.
I refuse to lie when asked that question. It’s led to people I barely know being inundated with a conversation they never expected to be in, let me tell you.
In my old age, I have mellowed a bit, however. Now, if I ain’t doin’ all that well, an honest, “Lousy, but it’s not your fault” is my comeback.