re: what's the secret to keep gas grills from flaming up?

It'll happen. Really no way around it. Particularly if you cook steaks or ribs, something with a lot of fat that will drip off it. That's what starts it.

If you have a lid for your grill, use that. That'll keep them to a minimum. But if you're cooking in open air, those flames will feed off the oxygen.

ETA: and when grilling, don't have your flames jacked up to the moon. Have it around medium heat. That'll be perfect.