[PvK]

First decide whether you want to risk the friendship for the chance or not, because it could mess it up.

If so, then resist temptation to reveal feelings you already have. Ask her out as casually as you can, and don't let her know you you already _really_ like her, until it's demonstrated she _really_ likes you back. Generally she'll want to develop affection _with_ you, and not to know about any feelings you had before you were going out, as that tends to just scare girls or creep them out.

PvK