10:30 am, commuter train to New York City: Before sitting next to me, a stranger set his briefcase down on the seat so that it flopped partway onto my lap. He didn’t move it until I looked at him balefully. Then he apologized and repositioned it. Once seated, he sipped from a styrofoam cup of coffee or chai latte or whatever, then placed the cup on the floor, continuing to reach down occasionally and sip again. I’m keeping an eye on the cup. My nice cloth backpack, also on the floor, will stink forever if the cup topples and the whatever spills.

By the way, I’m typing these words with this stranger inches away, and I have no fear that he will look. Only we writers are nosy enough to care what our train neighbors do.

He just pulled his Wall Street Journal out of its plastic sheath and stuffed the plastic wrap behind him into the crack between the seat bottom and the seat back. I am almost certainly getting off the train before he does, so I won’t see if he removes the plastic when he stands up, but I am willing to bet he won’t. Ditto for the styrofoam cup. Maybe I’ll find them on my return trip. Or maybe before I leave I’ll be crazy enough to tell him to take his trash with him.

A few other details, because I don’t want you mis-imagining: gray suit, pale blue-and-white striped shirt, blue-patterned tie, shiny black shoes, gray hair cut short, probably in his fifties, tall, fit. When he was speaking on his blackberry a minute ago, very terse, soft-spoken, thank heaven.

Later, back home, in my office, hour irrelevant: I did get off the train before the stranger, and I issued no warnings. But there was a morning when I scolded someone. It’s a little embarrassing.

My routine when I take the train is to meditate and then to write, but often I fall asleep – especially delicious, the sleep that follows meditation. I was snoozing happily one day, when two men approached my seat. Through my fog, I heard them discussing, loudly, where to sit. (The train wasn’t crowded.) They decided to put themselves across the aisle from each other so that, they said, their legs wouldn’t be cramped. One sat next to me, I suppose because I’m too small to cramp anybody’s anything. For a few minutes the two exchanged loud pleasantries then lapsed into silence, which did me no good since I was wide awake.

I was absurdly angry but too cowardly to want an extended argument, so I waited till my stop came to tell the man next to me that he’d been rude and explain why. His response was that I should do my sleeping in bed at night. No remorse. No apology. And maybe he was right.

The point, of course, is character development. I could invent the lives of these three men. I could put them together and see how they rub against one another. (They just happened to be men, no special significance.)

While walking through New York City today I saw a man (male again) in a business suit and a cotton billed cap. What was up with a suit and a cap? I can speculate: Maybe he has 365 hats, all in different styles, and wears a fresh one every day. He throws each one away at night because by now it’s (ta da) old hat.

But if he’d sat next to me on the train I would have had more fodder for my guessing. People in close quarters tend to reveal themselves. On the train they talk on cell phones, ease out of shoes that pinch, play solitaire on their computers, leaf through magazines or read serious novels, and occasionally start an actual conversation.

So you might try cramming your characters together – in an elevator, a closet, a bank vault – and seeing how they react. You don’t have to work this into your story; you can do it on the side. A character who’s been holding out on you might reveal her inner nature if she’s trapped with three strangers in the back of a truck.

In my train anecdotes I was a character too. Coffee-or-tea man this morning could have been deducing about me too. What would he have learned (without reading from my laptop)? He could have seen without reading that I was writing prose, not making entries onto a spreadsheet, that I wore jeans rather than business attire, even that I think ahead, because I took out my subway Metrocard before leaving the train.

Watch yourself from the outside for a day. Spy on yourself just as you may spy on other people. What are your characteristic behaviors? Our own personality leaks into our fictional characters no matter what we do, but this time make it conscious. Deliberately give a character a characteristic that belongs to you. Put her into a confined place and use that characteristic to get her into trouble.

Have fun, and save what you write!