When Harry finally landed Sally in the movie, it wasn't with flowery words or grand gestures. All it took was a little honesty --"I've been doing a lot of thinking. And the thing is, I love you."
If you've been pining away for your friend in silence, you have two choices: Keep your feelings to yourself and hope that one day she'll magically begin to see you for the amazing guy you are. Or, take the risk and tell her how you feel.
Before you make the leap, it's a good idea to dig around a little. See if she's interested in anyone else. Look for signs that she might like you (like staring into your eyes a little bit longer than usual, or being especially touchy-feely). Ask some of your mutual female friends if they think you've got a chance (unlike guys, girls talk about their feelings with friends).
Then, once you get up the courage, just ask her out! Go into it knowing that there's a chance she'll turn you down, so don't be too disappointed if that happens. But if she does reciprocate your feelings, your honesty will have started a whole new relationship, and who knows where that might lead?