How do i help for Ford Sync hear my demands better?
My wife has a Fiesta with the Ford Sync system and she had a similar question when we first purchased it.  When she was giving voice commands she was directing her voice to her iPhone 4, either by holding it up to her face or holding it in front of her.  The problem though is that the Sync system uses a microphone built into the car, not your iPhone, for receiving voice commands.  I'm not at home so I can't say with 100% certainty but I'm pretty sure her microphone is to the left of the rear view mirror.  With that said the location may depend on whichever Ford model you have.

I would check the Ford's owner manual, it should show the location.