“Slowly run your hand down the side of the tank, noting where it feels cold—that’s where your propane level is,” say the Longo sisters. Curious about the science behind it? The trick works ...

This cool zone reflects your propane level: If most of tank feels cold, you still have plenty of fuel. But if most of it feels warm, it's time for a refill. Read more: 18 Popular BBQ Chains ...