Water Smoker
There are various types of water smokers. Simply adding a water pan to a grill and offsetting the coals is the easiest. This is the water smoker I use for turkeys, pork sholders and sometime hams. There is a charcoal feed ring that sits on a charcoal grate that holds about 6 hours of coals. Above the coals sits the water pan. Above the water pan are two grates one about a foot above the other. This water smoker will cook 2 turkeys, a turkey and a ham or two of anything medium big.
Off Set Grilling
There are a couple methods to this I like. Most obvious is the Texas smoker. On the Texas smoker the firebox sits lower and to the left (with the version pictured). Then on the 22 inch grill I have deployed a water pan. The coals sit infront of the pan. Once hot and water steaming (it helps to boil the water to get it to temperature first - then put hot water in the water pan) seer the meat first. Then steam over the water, which can have a multitude of seasoning in it, onions, carrots, celery etc. The box type grill with 4 legs is my dads. I was visiting and wanted to smoke a salmon. To create an offset smoker I used foil as a dam to keep the charcoal and wood in one corner. That way the salmon was not directly over the hot coals.
Then there is the smokehouse method. This is where a picture is worth about four Twitter Tweets, or a thousand words.