So I thought it might be worthwhile to follow up my ambiguous pronouns post with a discussion of another problem I see on Book Country (and in published novels -- I'm not singling out the amateurs, by any means).
Suppose you have a character who is a grizzled old man with a beard, and he's rail-thin, and he's a colonel in your fantasy army, and his name is Jim. Further suppose you have an absolutely clear picture of the guy in your head, though you've been kind enough NOT to infodump, and you haven't given us a complete description of him. (And really, no one should describe their characters down to the last wrinkle on said characters' foreheads. It's awkward and unnatural to read such descriptions, especially when the character is thinking these things, which are completely unnatural thoughts for a person to have. But I digress.)
So you have some scene with Jim. You use his name a couple of times, you use "he" and "his" correctly a couple of times ("correctly" as in "non-ambiguously"). And then you refer to him as the old man, the Colonel, and the thin man, because you're interested in varying the language.
People, don't do that. It becomes very unclear to the reader how many people are in the room (or command tent, or whatever) for this scene. It's not obvious that you're always referring to Jim. And if you have multiple characters and you're doing this with ALL of them, it can get really bad. We simply can't keep track.
Ordinarily it's not necessary to refer to one character by name or description so many times in close proximity. Ordinarily I'd advise you to vary the language (unless you're using a word like "ordinarily" for effect, as I'm doing here). But I'm going to go out on a limb and say that you shouldn't vary the language so much that you lose your readers.
Terry Brooks is bad about this. He doesn't overuse the characters' names, but he refers to his characters as "Valemen" when it's not necessary, or most irritatingly, to Panterra and Prue as "the boy and the girl" even though they're teenagers and Panterra is apparently old enough to have sex (see The Measure of the Magic or Bearers of the Black Staff -- or don't, as they're really not very good books).