I've got a character in my book that's pretty much the poster girl for "grim and stoic determinator" but I'm not sure how to write that without her coming across as a cardboard cutout. She's a pretty nicely rounded character but her personality kind of makes her seem flat. Any tips on how to fix that/avoid it?
Perhaps you should think a bit more about what is it about her that makes her who she is and why she is the way she is. Grim and stoic people have just as many distinguishing building blocks to their personalities as any other type. Whether you do it by showing her defining actions or memories or ideology, you can round out her character. Maybe take a look at some real life people who you could compare her to, and see what defines them as stoic or grim, for inspiration.
The things we say reveal a lot about our character and personality. I've found that i can round out a lot of my secondary characters in very little space with choice remarks. You might try going this route. You might discover that your character is a grim and stoic smartass and she's funnier than you expected, or some other neat character trait that you hadn't considered. Go to important points in the story and look for opportunities to add these little statements. Good examples of character building statements at perfect times often come from movies, so that's what inspires me to work this angle. Think about Han Solo's response to "I love you" or something in a favorite movie where the character completely reveals his/her personality by what they say and when they say it.
You should let your character's actions speak for themself. Even if your character doesn't seem to care too much she can for example be really protective if she cares about someone, then you let her shrug it off with a "that's what you do for friends." That way it won't really show your character's emotions, but it will show there's more behind her than "a cardboard cutout." Your character can seem unaffected by grief, but yet skip lunch and breakfast claiming she's "not hungry." Those little things make the difference between a well written stoic character and a shallow character. The thing about stoic characters (and people) isn't that they're not affected by feelings and such, they're just really good at controlling their emotions or acting neutral, or they deny feeling anything to keep themselves from getting hurt (or is that a little too melodramatic?). Maybe the people who don't seem to be affected by anything at all are even the people who are the most sensitive. Although a stoic person won't admit it openly show it their actions will most likely speak for them around the people they care about and/or trust. If you don't know how to write your character study the behaviour of people around you. Just do it a few minutes a day, because you really learn something from it and maybe you'll even find someone who is the perfect example for the character you're trying to write.
@Tara that's a good way of putting it. Also think of how your character acts when no one's around. Or if you're writing in such a way that the stoic characters inner monologue is available. They could really be torn inside about certain things, but try and keep it up. Showing some turmoil adds some dynamics to the character.
It ain't whatcha write, it's the way atcha write it - Keourac. Even dull can become powerful it's all in the wording. Tara and Mottahko give good advice. The inner workings of your character can reveal a lot, some of the best sarcastic comebacks are all in our head - privy only for the reader. That would allow us to see that though she doesn't go out of her way to say things, she still thinks them.
Stoic people tend to have some deep seeded internal issues to overcome(Or revel in), like St. Augustine and the dreadful guilt of his stolen pears I'd suggest you bring some of those into the mix to bring her to life. My 2 cents