Lynn, the threads you start turn into such interesting discussions!
How do you do it?
Karen hit the nail on the head, according to what my reading on point-of-view tells me. This is the fundamental difference between third-person-omniscient and third-person-limited: in limited, everything you write is actually happening inside a single character's head, while in omni, although you can see the characters' thoughts, the story is being told in a single neutral voice. (By neutral I mean independent of any one character, rather than having no opinion.)
So everything written in limited pov ought to be in the pov character's "voice", complete with opinions, turn of phrase and accent. There isn't really any firm border between "narration" and "introspection" - you're writing what the character sees (narration), what they think about what they see (in between), and what they think about other stuff that's been going on (introspection), all mixed up.
A really good writer, writing the typical fanfic with alternating sections in Clark's and Lois's points of view, would produce a distinct "voice" for each section, so that you could look at any paragraph in isolation and tell which character's pov it was in.
Going back to Laura's question - while I intend to try and do this with my novel, it's not something I'm at all interested in doing for my fanfic. It would involve writing in American throughout all my stories, and that's just not something I'm prepared to do. :p I'd rather practise writing as well as I can in my own style, and lose a few readers who can't cope with the characters' introspection having a British flavour, than expend a lot of effort going up what is ultimately a blind alley for me.
Mere
