Me personally? I try to imagine that one Awesome Scene - diving out of the window as the room explodes, or the dramatic car crash, or the crushing line of dialogue, or the reveal as to who the killer REALLY is - and then I start with that. Backtrack to draw the line how you get there - Okay, so we find out the killer's identity in the middle of a dinner. Clearly it was someone we knew, hence the casual atmosphere. Alright, if we knew them, how did we meet? It's someone we trusted, so it could have been a work contact. How long did we know them?
So on and so forth.
So on and so forth.