On the vents: top vent 100% open, use the three bottom vents to adjust temp. Your WSM will tend to run hot the first dozen smokes or so, so damp it down hard early or the temps will shoot up and get away from you.
Wind is your worst enemy, I wrap a welding blanket around my WSM to act as a wind break and adds a thermal layer.
In non-wind temps ranging from 50° and up I can run at 250° with two bottom vents fully closed and one open about half way for 20+ hrs. I get almost the same results using my welding blanket in gusty high wind with temps down to 28°.
Once you figure out your vent adjustments, just make a mental note of where they are set and you will be able to dial it in very fast from that point on. If you do make changes, make small changes and wait 10-15 min. after to let the temps stabilize at the new vent position. Otherwise you will end up chasing temps up and down and getting frustrated.
I have had my WSM for many years and it has never let me down once. It just does it's job and it usually works best when I just leave it the heck alone! lol