>>2964253Focus beforehand. It's harder to focus - manually or automatically - when things get so dark.
Bear in mind that not everything looks so flattering with long exposure. If you're out on a windy day and trees are blowing around, they'll turn into a blurry mess along with the water or whatever it is you're trying to extend exposure on.
The vast majority of filters will create strong color casts on your images, even the more hallowed ones that appear to be a few steps up from $30 throwaways.
You probably don't need a 10 stop filter for whatever you're shooting, unless it's in the middle of the day, and if it's int the middle of the day the light is probably not all that great unless its overcast. For most scenes, 2-4 stops is OK, and 6 is pushing it.
Remember that ND filters are a tool like anything else, not a crutch, and that having a "cool effect" in your photographs like misty water does not inherently make them more interesting. Always pay attention to light, composition and subject as you would with any other photograph.
