Well, I've never had anything go past the "I've-got-an-idea-for-a-story" stage, but lately I've suddenly had an idea that I wrote down last year start to blossom & expand. Especially the main character & his life seem to have suddenly taken on a life of their own. I've been getting it all down as quickly as I can. ;D
The bulk of the main story plot is already written down. The main thing that I've had trouble with is expanding those points, or fleshing them out, into a workable story...the filler.