Flare-ups occur when splattered grease or fat makes contact with the heat source and sparks into a flame. To prevent flare-ups, make sure your grill is clean before you start-even old grease splatters can cause flare-ups and charring. Make sure you perform the regular maintenance check-ups recommended by your grill's manufacturer.
When cooking meats, trim off as much fat as possible before grilling. This will prevent excess fat from causing flare-ups during grilling.
To tame flare-ups on a charcoal grill, keep a spray bottle of water handy and squirt the coals as necessary. If flare-ups occur more frequently than you'd like, temporarily move the food so it's not directly over the heat.
Do not use the spray bottle to contain flare-ups when using a gas grill. Move the food over indirect heat temporarily to avoid further charring. Close the lid and reduce the heat to control the flames.
If the grease fire burns uncontrollably move the food out of the way, to a plate if you have to, turn off the burners, and spray down the grease to put it out. Close all vents and close the lid, the oxygen within the grill will burn off quickly thus ending the flames. Let the lid stay closed for at least a minute then remove the grill grates. It's at this point that you'll need to re-clean your grill to remove burned on grease and soot from the flames. Once cleaned you can start the grill again, bring it up to cooking temperature first, then cooking cooking with your meat. If you've properly trimmed any excess fat from your meat and it continues to burn place foil wrap or a metal pan on the bottom rack under the meat to catch the excess grease.