Want to check a bag or sit by a window on your next flight? Click the button and pay the price. Want to deal with the empty pang in your belly in air? Overpay for a stale snack. Want collision coverage for that rental car? No? Don't you know that you can also be charged for the days the car is out of service while being repaired? No, I didn't know that, and I still decline.

I've just returned from a trip to Phoenix, and I am surprised that — despite all the upsell opportunities thrown my way — I remained on budget. My mood, however, was not as impervious as my wallet.

The warning of financial doom at the car rental counter had its impacts. I let out a cry when my uncle accelerated behind the wheel. I fretted when the car hit a bump no bigger than a baseball. Also, I filled the tank as close to the car rental return as possible, in a sketchy neighborhood where the other cars at the pump were weathered jalopies.

When I picked up the car, the rental agent had given me the opportunity to prepay for fuel. I declined that offer, too, in part because the formula as explained was so complicated, I barely knew what was being offered. But one thing was very clear: I could not forget to gas up. If the company refueled, the cost per gallon hovered around $10. "Someone with a big SUV forgot," my agent blithely told me, "and they were charged, like, $300."

It was a relief to return the rental car, with no damage and a full tank, and some money still in my pocket.

Then, after I tucked into my airline seat, flight attendants walked down the aisle with credit card brochures splayed out in a fan pattern while another urged us to sign up. Did I know all the benefits that could incur? No, I didn't know that, and I still decline.

Send your questions or tips to travel editor Kerri Westenberg at travel@startribune.com, and follow her on Twitter: @kerriwestenberg.