first thing I did when getting a new WSM was to make sure there were no major leaks around the different sections...check for out of round conditions with a tape measure and correct if needed, big air leaks= out of control temps.. I never use water, only an empty pan with a foiled top...
half of a weber chimney of lit coals placed on unlit in the charcoal bowl. Assemble cooker and put meat on cooking grates with all air vents wide open, once Im within say 5- 10 degrees below my target temp I close the lower air vents equally about 30% and keep an eye on it for 10-20 min to see if the cooker settles....my cooker generally settles in between 250-280 degrees doing this, poultry I leave the all vents wide open most of the cook …..I tried water once and hated the experience especially cleanup