Asked another girl out yesterday. "Nah. I don't like to walk in the city."

I feel like a creep, asking girls out seemingly on the spot. It makes sense to me to do that, though: I like a girl and would like to get to know her better in a more-or-less private setting (which walking in the city appears to me as, what with strangers all around, with none giving a rip about us two), so I ask her out. Fair, right?

I have no experience on the matter - all the girls I've successfully asked out were already no strangers to me in whatever setting - so I have no idea what's at fault here, and neither do I know whether to trust what they say completely (does, for example, "I don't like to walk in the city" really mean it, given that the girl's from a conglomerate city?). Knowing I'm doing stuff that's fine will at least make me certain that I'm not messing my own stuff up. I feel lost - which, I suppose, is normal given that I'm just starting - head-first, too. I don't know whether I should persist, asking any girl I like out, or set my preferences up differently.