The Future is Prototyping
First off, you need to read this entire post, Try and Try Again – Why Prototyping Matters over at Big Spaceship. It's fantastic, awesome, informative, funny, and best of all correct! I'll be posting more on my personal experience with this topic eventually, but for now here is my favorite quote from the post,
If action speaks louder than words, then prototyping must be doing the death-metal guttural scream right in speculation’s ear. Instead of spending time discussing possibilities, we can spend time actually making something work. The earlier you get to the trying, the better you can inform the design – from font choices and colors to advanced interaction and mental models.
Go read the whole thing.