I find it easiest to sit down and start typing, virtual rambling or so. The more I try to think about a plot, the less I actually get written.

I participated in NaNoWriMo a few years ago with a bullshit quote that turned into some fantasy universe from my childhood RPG sessions and pushed out 28,000 words in two weeks. I haven't gone back to it, but there's enough there to sprout other ideas and directions.

Mass Effect, on the other hand, seems to be contained in 100 word drabbles, due to all the plots and side missions my brain wants to venture into. :|