When some writers get a shiny new idea (SNI) they sit down and type up an outline for the entire story. Me? I so can't do that. I attempted an outline one time, but it didn't work, so I went back to what I do best. Wingin' it. Okay, well maybe not completely wing it, since I type up a rough query first before I start on the manuscript, but I definitely sit down with an open mind.
In my rough query, I try to come up with a blurb of my idea that shows the stakes and plot. If it sounds good--something I'd pick up and read off the shelf, then I move on. It helps me to write a short blurb before I get going and pass it on to my trusted beta readers to see if it's a story that intrigues them before I put too much time into something I realize completely sucks (I have been known to write a 50k MS in a month.)
When you query, a lot of times you'll hear things from agents like plot holes and stakes. That's why it is so important to establish these things when you start your manuscript, because they may make or break your chances at getting an agent. So don't be afraid to talk with your beta's about SNIs. They may be able to help you establish a soild plot and stakes.
So my writer friends, care to share how you establish plot and stakes for a SNI?