Which side is the gas cap on?

I travel for a living, which means I rent a lot of cars. I used to have that moment when I pulled into the gas station and suddenly realized that I didn’t know which side the gas cap was on. Then, I would crane my neck trying to spot it out of the side view mirrors.

Along the way, someone showed me a trick. On most modern cars, the fuel gauge icon on the dashboard has a little arrow next to it pointing to the correct side of the car. No more confusion. See the sample image:

Fuel gauge on dashboard

So go forth and spread the knowledge.