Hi Trevor and everyone,
I would also recommend downloading the Practical Photography guides from
www.photoanswers.co.uk/Advice/Search-Res...s/Free-field-guides/
The guides have tons of advice on all aspects of D-SLR photography and came free with various issues of the printed magazine originally.
If you are doing landscape/sunset photography Trevor then you should maybe look at adding graduated sunset and graduated blue filters as well. The ND filters I'd tend to use where you want to change a couple of stops from what is metered ... e.g. the classic use of an ND filter is to give a "silky" feel to a shot of water flowing over a waterfall or rocks on a river bed.
Have a good weekend!
John
  