I used to litter causually, without giving it much thought. I'd think nothing of stuffing a newspaper between my legs, under my seat on the train when I was finished with it. Or I'd toss a gum wrapper on the ground.
Then one day about ten years ago, I was walking down the street with my friend Joey La P and I tossed something on the ground without thinking. Joey got all over me. "How about a little respect, bro?" He didn't humiliate me, but didn't let it slide either. Since that day, I've been aware about littering (not that I didn't know it was a lousy thing to do before that). So much so that now I'm like one of those reformed smokers, vigilant, judgemental. I give people the evil eye when I see them blatantly throw their crap on the floor, although I am careful exactly who I stare at and for how long.
But I've become a righteous prig. What can you do? Mostly, if I'm really bothered, I just walk over and pick up whatever has just been dumped and, without saying a word, or even looking at the offender, place it in a garbage can myself. If I'm with a friend, I give them the ol' Joey La P treatment. "Yo, how about a little respect?"