My two boys keep theirs short from lots of walks, but Lily's were very long, so I just had a nail trimming session (which she did not like! But her nails were so long and curving that one leg kept getting caught in her ear hair whenever she had a scratch). I realised this is something I hadn't provided any info about in the Library so now there are some good links with pictures, on how to trim dog nails.
http://www.cavaliertalk.com/phpBB2/viewtopic.php?t=2421
http://www.cavaliertalk.com/phpBB2/viewtopic.php?t=2421