[carhill]

But how do you know whether or not it's a smart idea to take the final step and admit your feelings, or to simply realise that it's not to go any further that where it currently is?

Nah, just distance yourself from her a bit. Seem (or be) preoccupied. Look around. Lots of cool women around. Survey your domain. I was just watching a group of nubile young Singapore Airlines flight attendants check in. OMG, I'm moving to Asia

That's how you get out of or avoid the friendzone; feel your power of attraction and interest as a man. Let it out every time you gaze upon a woman in your domain.

Distance yourself, wait awhile, maybe a month, and then, without further fanfare, ask her out. If she says yes, that's one answer. If she says no, that's another. Accept her answer. Smile in either case and go back to surveying your domain.