So you're writing along. You've got a great, and I mean GREAT plot planned. The hero is just about to swoop down and ...
Swoop down and ...
Um ... cue the hero! Where'd he go?
He's still arguing with his sidekick over how dangerous it is to swing on vines? But they were supposed to already have resolved that issue! Oh, great ...
Sometimes, your characters just don't want to cooperate with you. You want them to say one thing, they say another. You have a character planed to be outgoing, they turn out shy. Your character decides that the surprise party you're throwing him is a complete bore. What did you do wrong?
Yep. I said nothing. You did absolutely nothing wrong. In fact, you can congratulate yourself. You made a character with a mind of his or her own! Your character is no longer just words on paper and vague ideas ... but a person. And let me let you in on a little secret - those are the characters that your readers will most likely connect with and enjoy reading about.
Of course, you may have a few questions. How can a character have a mind of their own? Aren't they just people you made up? Yes, you have a point. You did make them up, and they are subject to your whims and crazy ideas. However, you have given them enough of a personality, or some quirk that make you feel as though you know your character. When this happens, you'll know what they'd do in a given situation ... that you may end up ruining your planned plot.
What happens if you had a plot planned, and your character is ruining it? You have three options.
1. You can verbally force them to do it. Just write it in. Have no consideration for your character's feelings and completely ruin his uniqueness. The problem with this situation is that it will look forced to your readers.
2. You can let them do what they want to do and see where this takes you. This option can be fun, but it can also be scary, too. It is not for control freaks!
3. You can use setting/other characters/random giant birds out of nowhere to force your character to do it against his will. Just as long as his reaction to this is completely in character, and the method you use to force him into doing what you want him to do is not illogical.
If worse comes to worst, you can also try tweaking their personality, but that only works in the early stages of their development.
Now don't think that just because you have lost complete control over your character that it means that you have completely lost control. You still get to decide whether he wins or looses, and what sort of plot twists you throw at him. He just now has the ability to throw some plot twists at you!