I was recently asked, "How do you go from being a friend of a friend, and instead start a dating relationship with that person. In other words, how do you leave the friend zone once your feelings have blossomed into something more romantic? It's a dilemma for some because it's hard to get the message across to your friend-turned-love interest.
It seems obvious to say, but you have to stop giving off the "friend-only vibe". For instance, when you suggest getting together, pick date-obvious places. If you ask if (s)he wants to go out for something to eat, suggest dinner at a restaurant that is obviously romantic. Make your objectives clear by sending out flirty vibes when you do ask her/him out.
Flirt. Flirt a lot. Flirting is really doing things to show you're interested. Compliment one really nice thing about her/him; sit closely enough that your thigh touches hers/his; make a lot of eye contact.
The art to flirting is making your feelings known without becoming clingy or a stalker. You will know when you have gone too far when (s)he breaks eye contact or moves or leans slightly away from you. It may be only a slight move, but pay attention to it. If it's there at all, that's your key to take it back a notch.
Yes, there are risks involved. (S)he may not be interested in you in that way. If that is the case, the two of you will find out if you really are good friends. If so, your friendship will survive. If not, your friendship may deteriorate; but then, it really wasn't that great of a friendship after all was it? In that case, the friendship would have ended soon enough, whether you tried going after a dating relationship with that person or not.
If it feels right, act on your feelings. If you are giving off too many "friend vibes"; (s)he may not have the courage to make the first move, thinking it would be futile. And that would be a tragedy.