Where Do I Start?

Here's the question this time around:
so I know what my story will be about, who my characters are, what my characters do with their lives, what one of them wears right down to the designer, and what happens to them. I just dont know how to start it all off! any help?
It's always hard to start a novel. I know from experience. Whenever I'm having troubles, I write out an important scene from the story. If you're lucky, you'll realize it's a great place to start. Other times, it's too far in to be the beginning. So, think about what causes that great scene to happen. Can you start the book with one of those?
Here's an example.
Great scene:
I loved how his lips felt on mine, and how we could stay there forever. It didn't matter that the morning would come and tear us apart. He'd return to his family. I'd run off to work, blushing like a schoolgirl. For tonight, we had each other, and that was enough.
Beginning:
It's impossible to love someone when they're not meant to be loved. Romeo and Juliet were cursed from the start. Rose and Jack were on a sinking ship. And Drew Lansen was known for spending his free time with his brothers at their lake house. He was one of those family first guys, the guys who just didn't have time for love.
And yet, I still loved him. I loved the boy who was impossible to love.

It's not my best, but it still shows my point. Try to view your book as a whole, a movie of sorts. Fast-forward to the middle, pause it and think, 'What happened to get me here?' And no, your answer is not, 'I pressed fast forward!' Write the beginning so one day it will lead you to the middle.