An active character is one that takes action with the intent of reaching a goal. They do things because they’re trying to help, or at least do something. They don’t just react to their surroundings, but they attempt to control them.
The character doesn’t always succeed, but they strive. Not every character, but the ones we’re supposed to care about. Above all, the protagonist. They need not be the only one pushing an agenda, but your main character needs to be doing stuff of her or his own accord. They have to make choices, even if there’s strings being pulled on another page.
A character can be a victim of circumstance, but they shouldn’t be a victor because of it too.
Edmond Dantes was a victim of circumstance, pushed one way or another, until he was the one controlling what he did, and subsequently controlling what almost every other character did. Luke Skywalker was hesitant to leave Tatooine despite wanting to, until his family ties to the planet were charred and smoking – and it took until the discovery of Leia being on the Death Star for him to push an agenda instead of merely following one. An errand boy doesn’t cut it as a protagonist if they hold no decision over their actions. I had a character in a story who found himself in conflict that escalated over time, but the overall resolution was because another character had given him the means to succeed; he was nothing more than a glorified switch-flicker.
Not everything they do needs to be successful, either. You can have general flubbing, but you can also have a double-edged failure that at first seems like a success. Due to an old roleplaying background, I tend to refer to those moments as Complications. Cop gets the jump on the killer, only for his gun to jam. Pilot jams the sensors of an enemy spaceship, inadvertently causing a feedback loop on his own vessel. Girl buys a bouquet for her lover, but they make her girlfriend’s hayfever flare up.
One obvious instance where a character being directed works well, is when they’re being purposely mislead. Man gives a box of chocolates to a girl he likes after being goaded into it by his friend, but she’s lactose intolerant. The guy can either pass the blame to his friend, or own it himself, but at this point it’s a decision he has to make – and as the one that made the initial action by giving the chocolates, he is forced to take on some responsibility. The important thing is that at some point of the story, the character needs to own their decisions and take responsibility for their actions.
Active characters are a must.
Tangent: Fire station near work has some old fire-fighting uniforms on display, plus some other old stuff (like a 1930’s fire engine). The particular uniform that comes to mind (because it gave me ideas galore) is one I don’t have a picture of, but in a nutshell, the helmet is reminiscent of a suit of armour; the kind that a knight might wear. A knight fighting a fire is not too wild an image, especially if one pictures the source of the fire as a dragon. In light of the ongoing bushfires here in Australia, it’d be a lot easier to stomach if they could be attributed to a destructive creature that didn’t walk on two legs and talk.