I've gotten a lot of advice—meaningful advice, I want to add—about writing characters who will make things happen. You want a character who likes to drink too much, kiss the wrong people, and crash the most expensive cars. You want a character who will say the unsayable, or at least relish a good fight. What you don't want are passive characters. Depressed characters. Nice, well-mannered characters who would rather say nothing than say something cruel. These characters will slow down your story. They will bore your reader. They are good for nothing.
For the most part, I believe this advice is helpful, especially when the writer is new. You can avoid a lot of navel-gazing stories where characters think a lot while sighing in an empty room. But the more I write, the more contained I feel by the need to create characters who lash out and jump around. I like my quiet, sensitive characters. I like the sweet ones, the sacrificial ones, the timid and the shy.
So I've started creating characters first, without wondering how they'll benefit the pace of the story. I write the characters I want, and because I want them around, I also want to get to know them. If they end up soft, passive, or disengaged, then I try to find the limits to their softness, their passivity, their disengagement. If I'm successful, I end up crafting the perfect, imperfect situation to crack them. I know I sound cruel, poking pins into my gentle protagonists until they sing, and I'm going to sound even crueler when I admit that I find the whimpering song they sing is often satisfying.
I disbelieve the urban myth that if you put a frog in a pot of water and slowly turn up the heat, it will stay, placidly swimming, until it is boiled to death. No creature remains passive under all circumstances; at some point, it must attempt to jump free. And it is in capturing the precise temperature of the water when a character jumps out that captivates me.
That I've learned, in following this path, is that the vast majority of characters, of people, will act out under the most banal circumstances. You don't need a zombie apocalypse. A surprise encounter with road rage can do the trick. Life will make a victim, and a victimizer, out of everyone.