Soaking is only good for small wood chips or such things that would otherwise burn right the fark up and not make any lasting smoke to help with the food. In that case, it's usually best to put them in a foil packet or a box or something to smolder in and put the packet/box on the coals.
Soaking chunks or anything larger actually is counter-productive to making good smoke, because the Thin Blue smoke you want is produced by a clean burning wood fire, which requires the wood to be burning at a high temperature in order to burn off the volatile compounds released into the air. That is what the "flame" is, those compounds burning up in the heat. If they did not burn up, you would see a thicker, darker smoke filled with all those compounds that did not burn up...which as we all know is loaded with nasty distasteful stuff. By soaking them, you are making it harder for the wood to burn clean.
Now, for units like a WSM or UDS running a Minion Method burn, that uses just a few chunks scattered throughout the coal basket, obviously that chunk is not going to be hot enough to burn off those compounds, but the coals around it will help burn a lot of those compounds, and the resulting smoke is thin enough just from the reduced amount of wood to not affect quality. This is technically the same sort of thing as using a small packet of soaked chips. While they may not be burning as clean as possible, the amount of smoke produced is rather thin.
Think of a stickburner burning a few sticks at a time. That is a lot of wood, and they need to be burning clean. That is a whole different story from a couple chunks, or a small packet of chips. Another interesting stickburner comparson (think large stickburner like a Lang) is using green wood. As long as the fire is good and hot, when you toss in taht green wood, all that crap will burn off in the heat, still producing a thin blue smoke. If you tried smoking ina UDS or WSM with green wood chunks, well, that would not possibly burn clean at all and make for some nasty food. I suppose you could soak the splits you burn in those offsets and get similar results so long as you have a hot fire, but I don't know what the point would be in doing that...you spent all that time drying the wood, why wet it back up just to burn it?
The thing is to know about smoke and fire, and what kind of fire and smoke your cooker is capable of producing, then making the best smoke you can from the fire in that cooker to make the best BBQ you can.
Hope that helps.
Oh, one more thing...
Some folks have soaked wood in flavorful liquids, like wine seasond with herbs and such. Just food for thought.
Happy cooking!
