The amount and type of Smoke Wood that you use / add may also depend, at least partially, on your choice of charcoal.
I find that:
Many common, commercially-produced briquettes have some unique flavors built-into them. In these cases, less smoke wood may be needed because some/most of the flavor that some users want is already "in there", or maybe only requires the addition of a little Smoke Wood to combine in a desired way with the charcoal or avoid combining in a bad way.
Natural Hardwood Lump (I've used a locally-available brand, Royal Oak, and Cowboy) seem to be more "flavor-neutral" to me, and allow me to lay-on a heavy dose of Smoke Wood. (At least, MUCH heavier than I would use with regular K or RO).
Also, be careful about stifling your fire by closing-up the top vent on your WSM. Doing this can cause undesirable bitter smoke to choke-up inside your smoker and can give a burnt/off flavor. Learn to get your smoker going and throttle the vents at the bottom before things get too hot to control. I usually start mine up at full-open on all vents for about 20 minutes, then close down the one most facing into the wind to 2/3 open and the other two to about 1/2 open, after which it usually settles-in somewhere between 225 & the low end of 300 depending on wind, ambient temp, and how big a hunk-o-meat I'm dealing with. Then, if needed, I can tweak the vent settings a bit and I'm good for the long-haul.
In most cases, I like:
Pork = half and half mix of hickory or pecan and apple
Yard Bird = only apple, but a lighter "hit"
Beef = Oak or same as pork
Too much hickory can result in a "hammy" taste - some like this, me not so much (If I want Ham, I'll BUY Ham...)
Hope this helps