Start the coals or heat a gas grill for medium-high direct cooking. Make sure the grates are clean.
Lightly brush both sides of the bread slices with the oil. Put them on the grill directly over the fire. Close the lid and toast, turning once, until the bread develops grill marks, 1 to 3 minutes per side. Transfer the slices to a platter. When the bread has cooled just enough that you can handle it, rub one or both sides of the bread with the garlic, and serve.
Ricotta cheese (about 1/2 cup); jazz it up by stirring in grated citrus zest or chopped fresh herbs
Chopped pitted olives (1/2 cup) or capers (1/4 cup)
Grated lemon or orange zest (2 tablespoons)
Sliced apples, pears, or plums (1 or 2 should do it, depending on their size)
Anchovy fillets or smoked sardines (1 or 2 per slice)
Thinly sliced salami, prosciutto, or other smoked or cured meat (about 4 ounces, number of slices per bruschetta will depend on the size of the slice; for prosciutto, you might want to use half a slice)
Crumbled cooked sausage or bacon (about 4 ounces when raw)