If one more person today pretends I'm not here when I say "good morning" or "hello" or "have a nice day," I'm going to blow a gasket. Maybe it's a Monday thing. I don't really pay attention to weekly patterns at work, honestly. I should keep a calendarial tally of how many times people are rude during the week.
If you haven't worked with the public, you'd be astonished.
If you have...meh. Just another day at the office, right?
But really. I implore you. Please! When, during the course of your day, someone says "hello," respond by saying "hi" or "hola" or "hey there" or, my personal favorite, "ahoy-hoy!" Don't leave them hanging. And when they say "have a nice day," you should tell them, "you, too." Really. Dont be THAT guy or girl.
Common courtesy doesn't cost you anything. You're not out of pocket or out of time. And you might actually be that bright spot in someone's day (especially if you say "ahoy-hoy").
Let's all work together to make sure that common courtesy is aptly-named.