I spent 15 hours in a roomette on an overnight Amtrak train for $400. I made 4 mistakes I won't repeat on future rides.

I traveled from Denver to Salt Lake City on Amtrak's California Zephyr — a double-decker train. My previous Amtrak rides had single-story cars, so I was excited to step on board and hoped my room would be on the top floor.

It wasn't.

And although the views of Rocky Mountain National Park were spectacular from my room, I could see further out from the dining car's windows on the second story, and I longed for a room with a higher vantage point.

Although Amtrak's booking platform didn't have an option to select a specific room, Amtrak spokesperson Marc Magliari told Business Insider that you can call the contact center, speak to a live agent, and request a particular room if it's still available.

He added that family and accessible bedrooms are on the lower level, regular bedrooms are on the top level, and roomettes are on both levels.

My Amtrak ticket included three meals. An attendant came by my room to reserve a seat in the dining car for each. I had breakfast just after we departed at about 9 a.m. I chose the noon lunch slot and the 5 p.m. dinner slot.

I didn't get hungry between breakfast and lunch, but around 3 p.m., my stomach started growling. In hindsight, I should have packed snacks for the ride.

The train had a café car with snacks, beverages, and microwavable meals for sale, but I decided to save my money and fuel up at dinner.

Hungry and eager, I entered the dining car a minute before 5 p.m. The empty tables were set with mini flower arrangements that looked charming against the rolling canyon backdrop out the windows.

At the other end of the car, I spotted a handful of employees looking at me and talking among themselves.

"I'm here for my dinner reservation," I said.

One replied that I was supposed to wait for an attendant to announce dinner over the intercom. Embarassed, I apologized and started to turn back. They told me to stay and sit at the first table while another employee went to the intercom.

I'd had nearly a dozen meals in Amtrak dining cars before, but this was the first time I'd made this mistake.

Some stops on overnight Amtrak trains are long enough for passengers to get out and walk around the platform for a few minutes.

I typically take this opportunity to get fresh air and stretch my legs, whether sunny or snowing outside. But when this train made its final long stop roughly 15 minutes before dinner, I was entranced in a book and decided to stay in.

After dinner, I regretted not getting off at that final extended stop when I craved space to stretch out and move my body.

When I arrived in Salt Lake City around midnight, I was grateful for fresh air and open space.