write it, then leave it for a couple hours and go back and read it. Then it should flow.

Just blurb all your ideas out onto the screen in whatever order comes. Bare bones if you want, partly fleshed or overburdened. Then, as ricky says walk away for a while and see what happens when you come back.

I am with the other two. If you have the idea, get it down, the particulars can be arranged once you are 'feeling' it better. Otherwise you might lose the vision and then you will be annoyed at yourself