I screwed up.
The greatest problem I have with my current world is that it defies the laws of physics. Much of the story takes place inside a giant hollow sphere (aka the Hollow Earth theory or Pellucidar to us Edgar Rice Burroughs fans). The inside of a hollow sphere has no gravity, or I should say the gravity inside a sphere pulls towards the center. That means my characters would spend the whole time floating in space and I can’t have that.
Now, I could ignore the laws of physics. Most people wouldn’t catch onto the gravity bit so long as the story is good (and it is). The thing is, it disturbed me. I couldn’t get past it. So, I made it a part of the story. And it is a very cool part – at least it is in my head right now. There is a very specific reason why the laws of physics have been broken and at one point reality reasserts itself and the laws kick in.
Magic systems need rules too. I tend to see two types of magic in books, free magic and good magic. Free magic is abundant and simple to use. It requires very little. A spell, a potion, a magical object, is all that’s needed to perform the act. Harry Potter is such a magic system, but HP isn’t about magic so much as it is about Harry.
Good magic always has a cost. The first time I saw this was in the movie ‘The Golden Voyage of Sinbad’. In it, the sorcerer Koura (played by Dr. Who’s Tom Baker) ages every time he casts a spell. By the end of the movie he’s an old man, each spell seems to take ten years off his life.
Now that’s a high cost. And magic should have a cost otherwise everyone would be using it for everything.
In Physics, every action has an opposite and equal reaction. If your magic follows this rule, you will have a balanced system. Say you want to heal a mortal wound? What if that meant transferring the wound to another living being? Or if you want a mage to throw a fireball, the thrower should suffer from hypothermia.
Whatever world you build, magical or otherwise, keep in mind that you can’t get something from nothing. Everything costs something and the most important cost should come from the actions of your characters. If your character oversleeps, there is a cost. If she gives a bum a dollar, there needs to be reaction to it. If not, then there’s no reason to write about it.