How do you ask out a girl...

Over the counter? My favorite approach requires them to ask "is there anything else?" cause then I can respond "yeah: your phone number. Write it on the back of the receipt there." Or something to that effect. I don't like asking a girl on a date outright, I like to at least get her digits first.
But if she doesn't ask, I go for the next best thing - ask if she has email, she'll say yes, I say "Great, write it down for me... and go ahead and put your number down too" while she's writing it down.

But, since you're going right for the jugular as it were, I suggest being straightforward but laid back. As Omi-Cron said, don't overanalyse or overthink things. Just walk up, ask her out, set a time and a place, and be done with it. It helps to be uniquely funny and charming (whatever your definition of that may be) so you don't come off like every OTHER guy who might ask her out. I like insisting that we meet in a public place "so that I can run away if you're a psycho" ... but just do your own thing, man. Don't even wonder "what if she says no" ... just assume she'll say yes. No point in even trying, otherwise.

Jam it back in, in the dark.

Sorry man, that sucks. Though, I tend to blow off the whole "I have a boyfriend" thing, cause I've found that half the time, it's a weak excuse that girls use to see if I'm persistent. But that's only half the time, and only the girls around here (which, I might add, are crazier than the usual bunch.) My motto: stick around and show her how awesome you are, she might change her mind. If not, heck, not like you lost anything, right?

There's nowhere I can't reach.

I prefer asking "are you single?" rather than "do you have a boyfriend?" because the first is just a straight question with a simple yes or no. The latter has all sorts of implications behind it - for most girls, anyway.

This thing is sticky, and I don't like it. I don't appreciate it.