Did it come with a tank gauge? I got a Weber Spirit II - in Ivory which looks quite nice - and it's a good little grill but didn't come with a tank gauge, which is pretty cheap on Weber's part. Need to pick one up. They're $20 on Amazon.
That's a good tip. Though since it seems like the ultimate nightmare of gas grilling is running out of gas, so I was thinking I'd eventually pick up a spare tank.
I'm not so sure how well these tank gauges work - that is if we're talking about the in-line pressure type gauges. I quit using mine because it seemed like as soon as I noticed that the gauge wasn't in the green, the tank was a few minutes away from quitting. I don't definitely know how this works, and I'm too lazy to look it up, but I don't think a tank's pressure changes much as it empties. If it did, you'd constantly have to adjust where you set the regulator valves as the tank goes down.
That being said, they do work if you catch them at the right time. Like if you see it in the yellow after you're done cooking you'll know to fill the tank before using it again. But, if it goes yellow in the middle of cooking something you may end up finishing up in your oven. That why, like you said, having a spare tank is the way to go.
Edit: Okay, I looked it up... https://www.hunker.com/12000128/why-propane-tanks-do-not-have-pressure-gauges