George Germon and Johanne Killeen, owners of Al Forno restaurant in Providence, Rhode Island, swear the key to grilled pizza is to work quickly (don't let the crust burn!) and keep the toppings light.
For best results, use a charcoal grill. Create two sections on the grill's very hot back section and a cooler preparation section in the front by putting extra charcoal in the back and less in the front. Place fire bricks on the grill's surface to divide these 2 sections. Allow the charcoal to burn, then cool a bit before cooking to prevent burning the crust.
If using a tomato sauce, place in a pot on the grill off to the side, stirring occasionally.
Place one half of the dough on a lightly oiled flat surface, such as an upside-down cookie sheet; work dough until it stays flat and forms a round or square shape, about 1/4 inch thick. (Tip: Pull dough out, and allow it to snap back. Let it sit for a few moments, then pull it out again. It will hold its shape better this way.)
Once dough is in desired shape, pick it up and place it directly on the hot section of grill. With tongs, gently rotate dough as it cooks, 2 to 3 minutes, until bottom side is browned and dough holds its shape.
Remove from hot section with tongs, flip over, and move to cooler section of grill. Brush top (grilled side) of crust with olive oil, and add toppings of your choice. Return to hot side for a few more minutes. Continue to cook until cheese melts and bottom is crisp, approximately 3 to 5 minutes. Repeat with the remaining dough and more toppings. Serve hot.
SourceMartha Stewart Living, March 1996