OK, as Jonathan Saw said below in response to Stoopid Grill Question #2, "Sometimes, if your grill dirty, no matter how long it stays on one side the food will still stick."
I've got a gas grill (a fair-to-middlin' mid-grade one from Sears--never again!) and can never seem to keep the grates clean enough to ensure non-sticking. Yes, I preheat it on high for about 15-20 minutes to burn off the gunk in the middle area of the grate,and that scrapes off, for the most part. But food still sticks, even on that area and even after wiping with a paper towel soaked in canola oil. But there's still stuff along the outside (the grill doesn't obviously heat well on the outside) that won't clean off.
Is there anything commercial and easy to find that will help that's not hazardous to my health? Or should I venture to Sears and buy a new grill grate and start all over?