I've just been through that stage of writing I dub "outline panic". Outline panic comes after I devote some time to a new concept, enthusiastically write out several scenes, and then come to a screeching halt when I realize "there is NO PLOT here. None. What was I thinking?"
So today I started outlining for reals. I find I work best from some combination of letting the words flow, and having a clear roadmap for where I'm going. I still don't have an outline, but am getting closer to identifying what the various parties' goals and objectives are. Which goes a long way towards settling the panic.
What this looks like from the outside is me staring blankly at the computer screen, or holding my head in what looks like despair, jotting down a note here and there every thirty minutes or so. It's strange how it feels simultaneously unproductive and productive.
Have you experienced outline panic?