Just because you don't have a charcoal grill doesn't mean you can't smoke.
Grill smoking over charcoal is straightforward: Wrap the wood chips in foil to create a packet, cut some slits in the top, and place it atop your lit coals. But getting a packet of wood chips to smoke on a gas grill can be a bit more challenging. The first step is to place the chip packet directly on the heat diffusers so that it is as close as possible to the flame. But because these don't emit as much heat as burning coals, sometimes the chips still don't smoke enough—or even at all. The diffusers also don't offer the most stable place for the packet. Here are some tips for maximizing smoke and ensuring that the process goes smoothly.
1. DON'T OVERWRAP PACKET: Make sure you don't fold the foil in such a way that creates more than two layers; this will minimize layers of trapped air, which would otherwise insulate the chips from the heat and hinder smoking.
2. WIDEN SLITS IF NECESSARY: If the chips aren't smoking, use the tip of a paring knife to gently widen the slits on top of the packet to let in more oxygen and encourage smoking.
3. MOLD PACKET GENTLY OVER DIFFUSER: Heat diffusers are often shaped like inverted Vs. Take advantage of foil's flexibility so that the packet won't fall to the bottom of the grill.
4. IF NEED BE, DON'T REPLACE GRATE: If the packet doesn't fit easily under the cooking grate, don't bother putting the grate back. In most cases, smoked food doesn't sit directly above the chip packet, so the grate isn't needed.