I sort of outline. Not anything real formal, but just an attempt to group things together. What I do once I have a general idea is try to break the idea into a few distinct parts. Under those parts I'll list what action or snips of conversation I want to happen there.

For instance, for the Gravedigger fic I just wrote I had the following:

Idea: She's having nightmares re: Gravedigger
   -Booth thinks of past time she's had them
      *First time
          *wanted to make her feel safe
          *just held her
      *Second time
          *She's out of the dream first
          *He wakes up to find her gone?
          *Floor by bed, shaking with suppressed
          tears
          *Laughs shakily - didn't want to wake him
      *This time
          *Waits for her to wake up
          *his own nightmares about not reaching    
          her in time
               -"He didn't need a calendar to
                 tell him; he could feel it."
               -Wonders if she's noticed
                    -She needs to observe
               -"Almost lost her once and he
                 didn't even "have" her yet.
                 Then again, they never had
                 really been just partners
   -Comfort one another
      *"Both knowing it's a promise he'll keep"?

So that's what I do. Of course, sometimes there's things I'll end up losing or changing, but that's generally what I work from. Hope it helps.