When I first became a member here, I lived in an apartment and all my smoker/charcoal grills were at my GF's. I wanted to find a better solution to those crappy smoker boxes and aluminum foil packets that would infuse enough smoke in meat that you would actually taste.
What I came up with was this: A soup can with holes punched in the bottom with a small grate at the bottom. I took two lit briquets, placed them on the bottom grate, then filled the can with chips. Then, I placed the can on the top grate of my grill, added the meat. I typically got about 1/2 hour of solid smoke, which for smaller cuts worked fine. For larger cuts, I would refill the can for another round of smoke. Now here's what's important: the can worked best(at least on my grill) when the gas was turned off. If I had the gas on, the oxygen would reduce and the briquets would burn out. So essentially, this was a cold smoking device. Once the smoking was finished, I turned on the gas grill and finished the meat up with direct or indirect heat, depending on what kind of meat I was working with.
I don't use the can anymore, but for those who only have gas grills, or want to get some smoke flavor on your meat without firing up the smoker or charcoal grill, it works quite well. Depending on what kind of meat, I have used oak, hickory, cherry, pecan, maple, and apple chips.
Before any grilling or smoking takes place, it is important to always have a cold beverage handy:
Top view of can:
Can in action with meat on top grate:
Here's a sample of finished product: