I have also heard and read bout this countless times and sadly not practised it!
They say you must have a writing pad and pencil next to your bed when you sleep at night. So you can jot down the main points of your visionary dream
I guess its because i am always tired at night,bad excuse hehehe.
I always move with a notebook though during day time and have jotted down many ideas.
Incase i have no access to a note book,i just open my notepad app on the phone and jot it down.
Thanks foe this great reminder of why we need to act quick on great ideas else they disappear in thin air just the way they came!