I don't think it's an impulsive one-off, but what might come afterwards...like maybe suggesting food before or after the next time.
Someone here talked about how do you know when getting together with a new friend for a meal/coffee say, is or isn't a thing. if you're asking about that, I'm not sure. Maybe when the other person is hugely smiley and laughs at your pathetic jokes? Nods enthusiastically when you suggest going on somewhere else? Sneaks peaks at your arse? I dunno.
Seeing more than one person (I can't bring myself to use the D word..it's way too US of A)?
If you like someone your seeing, ask if they would mind?
Of course all of the above is pretty abstract...I haven't done much in the way of the straight-forward d-word myself.