You are not ready to "write," if...

if you can't complete this sentence...

"This is a _(story, essay, paper, novel, report)______ about 

___(specific subject, verb, etc)______,

and it is interesting because ___ (Why would anyone want to read it, and why are you writing it?)___.

Until you do this you have no "idea" what you're writing about. It may be assigned, or on your on.

This helps you with all the other "steps" of writing, but you may also find you change it as you do research and organize.

But, 

type this sentence, print it, tape it to the front of your computer, and you'll save time and do a better job of "writing."

--William Blundell, The Art and Craft of Feature Writing, and Terry Clark, The Write Stuff.