Kristina,
Excellent advice (as always) from Michelle. I just want to add another link.

Although I've never used the Snowflake Method from scratch, I find steps one through six a great way to go back crystallize my ideas once I've worked on them a bit. Step one is in fact what most writers would consider a premise, even though I don't think the guy who invented the method calls it that.

To that end, I keep this link   handy to refresh my memory on the Snowflake Method. It gives a quick look at all the steps, and uses The DaVinci Code to illustrate the first two steps.

...
Regards,
Eric Fretheim

"It is perfectly okay to write garbage-- as long as you edit brilliantly." ~C.J. Cherryh

"Success is the ability to go from failure to failure without losing your enthusiasm." ~Winston Churchill

"I write one page of masterpiece to ninety-one pages of shit. I try to put the shit in the wastebasket." ~Ernest Hemingway