Rule #1 When Buying a Used Car: Trust Your Gut.

I'll give you a little example. Recently, the folks at Time Inc. asked me to help with a food truck project. I can't say more than that at this point, but suffice to say that I scoured the local Craigslist ads in search of something suitable. A colleague was on the hunt, too, and found one he thought looked good. In the photos, it did look good. It had tables set up in front of it, the interior was clean, and its white paint shone brightly in the sun.

I wasn't the one who called to inquire about the vehicle, so I didn't get a chance to talk with the owner. I was only along as a technical adviser, of sorts. When we pulled up where the truck was parked—in a less-fashionable corner of Bridgeport, Connecticut—my heart sank. There was the truck, shining less and listing to the side more, amidst a jumble of rusty car parts and what looked like an odd assortment of discarded carnival ride sections. Weeds poked through a chain link gate that hung lazily on its hinges.

The seller didn't answer his phone. A pair of guys walking slowly across the street with an old table between them paused to see what we were up to. A UPS truck careened around the corner, turned around, and retreated. This, I thought to myself, is not going to be a good buy.

The seller—or rather, the seller's sister, who was taking care of all the phone communication on his behalf—didn't call us back until we'd scarfed down half of a clam pizza at the Frank Pepe Pizzeria in nearby Fairfield. Come on down, she said. My hopes did not improve.

Arriving at the lot, I noticed that the gate had been thrown open and was now leaning out into the sidewalk. Parked in front of it was a light blue BMW X3 that looked like it had come from an auto auction. You know, the sort of nice car that just doesn't look right. A fresh-faced young man sporting decorative black and white patterned sweatpants, a backwards baseball cap, and one partially shaved eyebrow greeted us with a charming smile.

"I didn't know y'all was coming so quick, else I woulda had this thing done," he said.

What he meant by "done" became readily apparent. My gut had told me the truth. The stairwell in the old box van was nonexistent; it had rusted into thin air. The interior, where I assume food had once been prepared, smelled of urine—animal or human, I couldn't discern. The engine was caked in oily grime and the carburetor was covered with salt splotches. The young man wasn't sure if it was a V8 or a V6. (It was a Chevy V8).

"I bought this all the way up in New Hampshire for nine grand, but I, uh, added a $800 generator an' shit, and it made it all the way back here," he said, by way of explaining his $13,000 asking price. Apparently, his truck transfer and generator-purchasing skills came at a premium.

My mind having long been made up to seek other food truck candidates, I asked, out of sheer curiosity, if he could fire up the engine. I asked several times, actually, but he deflected my request with the skill of a politician dodging a tough policy question. We never did hear the old beast roar to life.

I told him we'd let him know.

Say what you will about time wasted. I'm grateful for the rich cultural experience the excursion afforded. As for the next trip, I'll arm you with the same questions I should have told my colleague to ask before we set out to travel nearly two hours for the pleasure of seeing a giant metal turd. These questions can save you some time, too.

1. Does it run?

2. I said: Does it run?!!

3. Is there any rust?

4. When's the last time you drove it?

5. Why are you selling it?

All of this is a way of asking, sotto voce, "Are you a trustworthy person, or a scumbag?" Your gut will evaluate the tone of the seller's voice. Make sure to listen carefully to the answer.