If your grill has grease burnt on it, you'll usually need to spend time aggressively scrubbing it with steel wool to get it clean. For an easier way out, you can try Stylelist Home's advice and dump unused coffee into your grill.
Since coffee is acidic, it works great for cleaning up grease, and the process is about as hands-off as cleaning a grill can be:
Brew a full pot of coffee, pour it into a basin and then soak your grill grates. (This also works for barbecue utensils or oven burners.) Let it sit for about an hour, give it a quick scrub and then rinse with warm water. The grate should be good as new.
While we'd never suggest you waste a good pot OF coffee just to clean a grill, it's certainly a good use for an unused pot you didn't have time to drink. If coffee isn't your thing, then you can always clean a grill with an onion.
How to Clean a Grill with...Coffee? [Stylelist Home]