Choosing characters for you story can be hard. You have to make sure they fit the role, that they are the way you want them to be, but you have to be prepared to change them for instance:
Mary: serious, intelligent, truant (see how the last trait contradicts the first two?)
Anne: pretty,(pretty can tell yo what the person is like), kind, rebel
Jane: head girl, hard studier, punk
I'm not saying that these traits can't be possible and are strange, because the whole point is that people aren't simple. You don't want strait forward characters for your story, unless they seem straight forward, but have chaos lying in them.
But here is the hard truth.
Your character will change.
Don't fall in love with them. Wait, do, but don't hesitate to change them slightly. But you shouldn't deliberately do it. Bear in mind that they will change, and they will. But if you find they have changed, that is good. What ever is happening should change them, but if they aren't, don't panic, as long as you are not forcing them to do anything, they will be the way thy are supposed to be.
Anyway, back on topic.
Okay, so you don't know whether to make Mary, Anne or Jane your main character. Or maybe you know what your character is going to be like, but you can't decide on a name. This is all right- just settle with a name- and that is harder than it sounds- that either fits well, or if very neutral, like Mary, Anne, Jane, Sarah, all popular, beautiful names, which can be bent to many personalities.
So consider the names. What is in them? Who do you know with that name?
Perfect Adventure character:
Sarah, Courageous, curious, strong, many skills
But if your character is like this, what is the story going to be about? You can write a story like this, (Indiana Jones) but it doesn't have the same depth as if you develop the character through the story.
Why not? Because Your reader will feel they know the character better- they have seen them grow. Because, they are going through an amazing experience, it will change you. It doesn't have to very much, just liek a perspective on something.
For example, In The little mermaid by Hans Christian Anderson (You can read it on the blog) At first she is very curious about the above world, and then she finds a man who is in trouble. Some say she rescues him because he is handsome, but in the original, it is because he is strange.
And then she follows him. Her curiosity is now desire.
And she gives up everything to be on land, and then, she gives it all up. She gives up what she gave everything for, because her perspective has changed- it is not worth killing her love to have what she wants- he is the one thing that she will not give up for herself- so she dies.
Get the gist?
Choose your characters carefully, because if you choose the wrong one, you may need to change them halfway through, and that can be painful.
So choose carefully.
Also, choose the type carefully. The princess and the frog would completely fall apart if the frog were a piranha, and the princess in most fairy tales would die off if they had not been princesses.
Good luck writing!