I open all the vents fully till the temperature gets within 50 degrees of my target then start closing the lower vents down. Most of the time I end up with two vents fully closed and one cracked about 1/4 of the way. It just depends on the day and the current conditions. Once it settles on target I don't have to make many adjustments unless there is a major change in ambient temperatures. Leave the top vent fully open, the only time I close that is if the temp shoots really far above my target and you never want to close it completely unless you are killing the fire..
For most cooks with my 14.5 I light 8-10 briquettes. I fill the charcoal ring, usually completely unless it is a really short cook. Then take 8-10 briquettes out of the center to make a bit of a concavity which I pour the lit coals into when they are ready. This usually gets me up to my usual target temps of 250-275 relatively quickly. I can get about 10-12 hours with Weber briquettes without needing to add more.
I used water for the first few cooks on my 14.5 but if you aren't paying attention and it all evaporates the temp will shoot up really fast, and it is a pain to refill. I don't bother with water at all anymore and find it much easier to maintain heat at a constant temperature. I have a clay saucer that sits in the bowl and I cover the whole thing with foil to catch the drips for easy cleanup.