Don't even say it if you *do* mean it, unless you want her to start assuming that you're going to move in together, get married and have kids. In my limited experience anyway. And once you've said it once, it'll break her heart if you don't say it at least once per day thereafter.

With me - I did mean it. BUT - I didn't want to get into an actual serious/long-term relationship for various reasons. However that's the expectation that was created (she had our whole lives planned out within about 5 minutes including how many kids we'd have and was straight onto babynames.com), and it was difficult to backtrack. If you do make that mistake, let them know early so that you don't string them along.

I think it's a matter of defining 'love'. I love my male friends, but that doesn't mean I'm homosexual and it doesn't mean I want to marry them. If you say you love a girl, they tend to use the "you're my soulmate, let's get married" definition. Be careful.

As I recall, I think she said it first in my case. It's such an awkward position to be in - you tend to feel pressured to say "aw, I love you too" so that you don't hurt her feelings. I don't know any decent cop-out for that... I'd probably just say "aw, that's nice" and if pushed on the subject then admit that you're not ready for the commitment that the 'correct' response would imply. Might hurt her a little, but better than stringing her along letting her think you're soulmates then admitting it 11 months later.

The poll results so far are spot-on: Either "Never" or "Every day" - whichever is appropriate to how far you want to take things.