Unless you're building your own coils, a lot of it is trial and error in terms of finding the sweet spot for a particular atomizer or even a particular coil. That's the beauty of adjustable mods.
Start low and work your way up. When you reach the point that it's starting to burn, back it off a bit. For example, when I was vaping on protanks I found that they worked best around 6 or 7 watts--long, airy draws. My current kayfun builds work best above 12 watts.
Sometimes the dry, burnt hits are a result of the atomizer not wicking enough juice.