How do you get a girl from just wanting to be friend's to wanting to go out with you?

You and girl are already good friends, you share a level of comfort-ability with each other. So telling her your feelings should not be much difficult.

Liking is a loaded Word, it could an infatuation, platonic pull, instinct, or even the romantic love. Be sure about your feelings before making the move. When you profess romantic love to someone , its entrusting a life with the person.

Most of the times, people try finding out reciprocability of the feelings, to be sure what the other person feels. Its not important. Even if the other person does not feels same for you, you make yourself lighter by sharing your feelings.