Basically, if she likes you, chances are you will have come up in conversations with her other girl-mates from time to time (e.g. You did XYZ & etc.). If it's a particular close friend (and she "approves" of you), she may even bring the subject up about the two of you herself. Otherwise, you can steer the conversation towards her (the girl you like) and gauge her (the friends) reaction... and that would tell you whether or not you stand a chance.
I appreciate this is easier said than done, but for the time being, try and let go of all these feelings & fantasies of what life would be like with the two of you as a couple. Focusing on those will only get you worked up and too nervous to ever ask her out, and then if (shock-horror) she does blow you out, it hurts 100 times more (i.e. the dreaded "Paralysis by Analysis" scenario).
If & when you do make your indecent proposal, I would suggest doing it casually, rather than making a big ceremony out of it. What I tend to do is get a free-flowing conversation going (i.e. one where you're not thinking about what to say next, and no awkward silences etc.) and then steer the conversation to social things in general, and then say something like "
I heard there's this new bar down George St, it's supposed to be good, we should check it out after work sometime".
I like to keep things casual, as if too big a deal is made of it, then she may feel like she's being put on the spot, and may end up saying "
No" simply to get out of an awkward situation... only to kick herself later on at a missed opportunity. Trust me on this, I've done this myself on too many occasions I care to mention. The other thing I'll point out about the example above is that you'll notice, I didn't '
ask' her (per se), but it was more of a statement. I'm sure you've heard that girls (and guys) are generally attracted to self-confident people? The example has a far greater sense of confidence and assurance than if you were to say "
Do you want to go to this new bar on George St?" After all, if you've already got a good rapport going with her, you can naturally assume she'd be happy to spend time with you outside work.
Anyway the key thing is to make a commitment to get the date soon, as crushes tend not to last forever... And in the meantime, don't dwell on all the fantasies too much (well maybe the odd "
knuckle-shuffle"
).