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.
The first thing you have to do is get it home safely. (I laughed and laughed when I heard this story). Apparently there is a vacant lot on the corner right next to the local WalMart. The employees at WalMart call this lot the Grill Eater Lot. There are several smashed up grills that ended up dumped in that vacant lot as their owners took the corner too fast and lost the grill out of the back of their pickup trucks (I totally need to drive over there and get a picture). So – a tip for the new grill owner – tie it down before you leave the store :-).
Brush your grill grates after every use (inspect for wire brush bristles before cooking), and thoroughly clean them every couple of months, depending on grill usage. And twice a year, you should give your grill a thorough cleaning, which helps it cook better and last longer. The basic process is the same for gas or charcoal grills; charcoal grills just have fewer parts.
After about 30 minutes, turn the heat off and let the grill cool down. Wipe things down to remove any lingering residue and you should be good to go. The grill grates should have turned a bronze or dark brown color if they are metal or a darker brown/black color if they are cast iron. For cast iron grates, the oil will have penetrated the pores of the metal and created a smooth non-stick surface that will be perfect to cook on.
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. 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.