This is important, and it very much depends on the type of grill. Some people advise burning off excess fat and grease to make the grill easier to clean. Some suggest using a stiff wire brush on cast iron grills. The problem with that is that several modern versions have an enamel coating, and a stiff brush could ruin it. The only safe course of action is to follow the manufacturer’s instructions carefully. Companies know you don’t want to spend all day on the chore, so most will offer methods that make cleaning as easy as possible.