One or two tips I've picked up over the years. . .
First, close the lower vents about 75%. No need to be very precise, just close them a bunch. I found that with the bottom vents wide open controlling temperature with just the top vent was very tough, wide swings. With partially closed lower vents, however, it is much more stable and you can move the top vent a lot without having huge temperature swings.
Second, toss the water bucket out completely. Put a Weber or other foil drip pan in the bottom and fill it with HOT water (so it doesn't act as a heat sink). You can never keep the little pan above the coals full, it's worthless.
You'll get good cooks out of it following the directions with these two tweaks. Enjoy!
Noble Knight of The Veg Table, Proud member of BOTOC