Grilling purists love cooking over charcoal. It takes some work to set up and heat the briquets (and you have to deal with the used ones at the end), but charcoal gives meats and vegetables a rich, smokey taste. Though gas grills don't contribute as much flavor, they light with the press of a button and require only brief preheating, so you can start cooking in a matter of minutes - a definite bonus when you have a crowd that's ready to eat.
Make sure you have a full tank of gas or a new bag of charcoal and something to start the briquets with (see preheating sections for options). Check the tank gauge on your gas grill, if it has one, to see if you have a full tank. Since the gauge works by the tank's weight, you can also lift the tank to check; if a tank feels empty, it is. Use a fresh bag of charcoal for the most consistent results; once a bag has been opened, it doesn't burn as well.