Most gas grills are hot enough already, even using a charcoal one can be hot. But if you're having trouble getting it hot enough to cook your food on the grill, then just add lava rocks around the burners.
It won't make the grill any hotter but it will retain more heat under your cooking surface. The tip comes from Top Chef vet Preeti Mistry while talking to folks over at Chow.com.
To do this, you'll need expandable grill grates that are easy to remove and replace. Line the lava rocks up and pack them closely enough and fire up the grill. Wait about 20 minutes or so, and your grill will be ready to go.
The lava rocks retain a ton of heat. And heat is what you need to make delicious meat because it's the Maillard effect.
Over time, those lava rocks will start to get covered with rendered fat, so you'll have to flip them over when they're covered. Give it a shot!