The all important first line

Many people choose a book based on its first few sentences or even the first line. One of my favourite first lines is 'It was 7 minutes to midnight.' (Mark Haddon, Curious incident of the dog in the night time). I love it because it's such a simple sentence and yet it's so precise. I also like how he writes the number '7' (rather than the word), which hints at the narrator's obsession with numbers.

Trying to come up with a killer first line is, well, liable to kill you! But I think often simple is best, as with Haddon's example.

I've yet to come up with my killer first line. In fact, now that I've decided to include a prologue, I'm not even sure where my first line is! Here's the current first line of the prologue:
'Do you ever think about it? About what happened back then?'

And here's the current first line of chapter 1:
Tash twisted the small silver mirror in her hand.

So how far away am I from 'killer' status? I'd like to know what anyone out there thinks.