I think I'm going to take Delta's approach. >_> Just ask. If its a yes it will be 1.2 seconds of happiness and an instant "Holy shit now what." following. If its a no it will be a smile, an "ok", and I won't have to worry about this damn thing anymore. >_>
No, no, no. That's exactly what you don't want to do. If you ask a girl out, always have tentative plans in mind. It doesn't have to be anything elaborate, but at least a general date and a general idea to suggest. It can even be the entirely predictable first date of a movie that fri/sat night (although I'd recommend something more creative), just make sure you have something.