[wavemachine]

Your on the track to how I use them, you say you are using an ND4 is this an ND Grad 4 or an ND4.

What I tend to do is:-

Setup tripod and Camera using a hotshoe spirit level and use a remote or cable shutter release.

Switch camera to maual and set required aperture and set shutter speed according to the lightmeter line on the LCD.

Double check viewfinder (composition) and set focal length and focus manually or use auto focus on a set point and switch auto focus off.

Check IS is switched off if thn lens has it otherwise IS can get confused on a tripod.

Set shutter speed 2 stops back for an ND4 (you can find stop charts on the internet and there is a great IPhone app called "Longtime Exposure Calculator" to make live easier.

Take shot review on screen and histogram adjust shutter speed accordingly and take another shot if necessary.

If you are using graduated it is the same as above although you should not need to adjust the shutter speed, make sure the lines on the grad filter are level and only come down as far as you need.

Oh and if you are using a wide angle lens carefully check the corners aren't obscure by the filter system, if you can't avoid it then ensure you have room in the frame to crop it later.

I did a one to one with a pro and he did it pretty much the same way.

One final thing is invest in a circular polarizer as these bring out the blue in the sky and reduce reflections and can be stacked with ND filters also.