I use maple, oak (no bark .. oak bark loaded with tannins), hickory, mesquite or apple in chips or small chunks. Place 2 bricks on side-edge onto the inner bottom of grill, such that they resemble hands on a clock face at (for example) 1 and 4 0'clock. It will be into this triangle that you put your hot coals. To smoke a fryer chicken, simply put the wood-for-smoking onto the coals, then put the upper grill in place, with the bird on the OPPOSITE side of the grill (above 5 to 12 o'clock). I do not use any spices at this point. Open all the bottom vent holes. But be sure to leave the lid/upper vent holes closed. Put the lid on firmly and walk away. Smoke should continue to issue from around the periphery of the lid. The smoking wood supply should be checked in an hour or so, and supplemented if needed. Otherwise, the chicken should be beautiful and ready with chocolate-brown skin and moist inner flesh....by 2.5 hours.
If you use fish (whole), pre-marinate overnight in a brine (1 gallon water; 1 cup kosher salt; 1 cup brown sugar; 4 bay leaves
; 1/2 tsp chile powder) in the fridge. Drain, and rise with fresh water. Place fish as you did the chicken on the upper grill surface. Smoking time varies, depending upon the thickness of the fish. Also, .... consider that the more coals you use - the greater the heat. So, be careful to not "cook" the meat before a good smoke-effect develops. Another tip: After I rinse off excess surface brine before putting fish in grill, I dry the fish with paper towels, and rub cooking oil over the surface. This will help to avoid drying-out of the flesh.
I have used this method for lake trout (my absolute favorite of all fish to smoke, but here I now sit (sob) in Florida....instead of Michigan's Upper Peninsula, which I dearly miss, and where lake trout was so easy to acquire), salmon, whitefish, pike, bluefish, mackerel, croaker, and others). Remember: size DOES matter. The smaller/thinner the fish: the less time to smoke-completion, and the less brining time (reduce to 6 hours) for little fish or big filets. Your only enemy is the chance of drying out the fish. So, monitor them in the grill as time proceeds. The whole point of the method is that you don't need an elaborate smoker.....you just need a (large size) Weber grill.