Reassemble the grill, then turn it on to its highest temperature setting and close the hood. There may even be a cleaning level on your burner dials. After a few minutes, open the lid and scrape the grates vigorously with a non-bristle metal grill brush. One I particularly like is the $15 Grill Bristleless Scraper from Taylor. This brush has multiple surfaces and edges to attack and remove grime from grill grates. It even has a handy bottle opener. 
Check the fuel lines for visible defects. If any fuel lines have unmistakable damage (like rips, holes, cracks), replace the parts immediately before your next use of the grill. Also be sure that any fuel lines have a smooth trail. You don’t want any of your fuel lines to be bent, because that will prevent the gas from flowing correctly. Check the exterior of the gas tank for any damage as well; things like dents, erosion, punctures, or any evident signs of damage. If you find areas that have obvious damage, you could potentially have a gas leak.[5]

If you're all right with all that and want to give this method a try, here's how: Pat the meat dry with paper towels and sprinkle both sides of the steaks generously with Kosher salt. Be sure to get the salt on the edges of the steaks as well. That's 1½ inches of surface you definitely want to cover. Press the salt crystals into the meat with your hands.
Prepare the corn. Trim the silk from the top of each ear to prevent it from catching fire and burning. Peel away the first layer of husks and remove the stalk end using a serrated knife to expose the bottom of the ear. This will make it easier to slide the ear of the husk, post grilling. (Optional: Peel back a 1-inch section to expose the kernels and char some of the corn.)
Re-assemble all the parts you removed, taking care to fix the burner tubes back in place in proper position with the cotter pins or screws. Rub cast-iron grill grates with a light coating of vegetable oil. Finally, re-connect your propane tank and fire up the grill; let it heat for at least 15 minutes, then turn it off again. This will help burn off any residues from cleaning, season cast-iron grill grates, and serve as a check that you re-assembled everything properly.
When the grill is cool, remove the grates and flavorizer bars and put them into a full bucket of soapy water. Let them soak for at least 15 minutes. Remove anything else from the grill that you can take off without tools, like burner control knobs and the grease tray. This will make it easier to clean. Most gas grill burner tubes are removable as well (look for simple cotter pins on one end, although some models use screws).
Check the fuel lines for invisible openings. Create a mixture of soap and water. Make sure you stir the mixture around so it gets really sudsy. Then, use a paintbrush to brush the soapy mixture onto the fuel lines.[6] Turn on the gas, and brush some more soapy water onto the gas lines. If any bubbles form on the gas lines, that indicates a gas leak. Immediately replace any fuel lines that exhibit signs of a gas leak.