Secondary (and tertiary and further) characters are every bit as important as your main character. Where the main character has to be the vehicle for her or his personal story — and more often than not it’s a story of exceptions — the secondary characters are going to carry your world. By having a wide and diverse cast of bit characters, you show your world as being rich and fully-formed. Characters will accomplish this impression of a ‘full world’ far more evocatively than any amount of trivia you might come up with. But, seeing as secondary characters by nature get less page-time than main characters, it can sometimes be hard to really express them as being vivid and fully-developed.
- Less is more – It feels hard to give your secondary characters as much development as your main characters because it is hard. It’s nigh-on impossible. And frankly, books that try it run the risk of getting too cluttered. So don’t. While your characters should be fully-formed to you, the audience should only get glimpses of them when they’re on the page. If they have their own character arc but we only get to see the start and the end of it, that’s fine. The impression that they’ve got off-page stuff we don’t get to see is going to make them feel more real anyway.