They start writing early, even before they think they are "ready" to write, because they use writing not simply to transcribe what they have already discovered but as a means of exploration and discovery.
They don`t try to write an essay from beginning to end, but rather write what seems readiest to be written, even if they`re not sure whether or how it will fit in.
Despite writing so freely, they keep the essay`s overall purpose and organization in mind, amending them as drafting proceeds. Something like an "outline" constantly and consciously evolves, although it may never take any written form beyond scattered, sketchy reminders to oneself.
They revise extensively. Rather than writing a single draft and then merely editing its sentences one by one, they attend to the whole essay and draft and redraft--rearranging the sequence of its larger parts, adding and deleting sections to take account of what they discover in the course of composition. Such revision often involves putting the essay aside for a few days, allowing the mind to work indirectly or subconsciously in the meantime and making it possible to see the work-in-progress more objectively when they return to it.
Once they have a fairly complete and well-organized draft, they revise sentences, with special attention to transitions--that is, checking to be sure that a reader will be able to follow the sequences of ideas within sentences, from sentence to sentence, and from paragraph to paragraph. Two other important considerations in revising sentences are diction (exactness and aptness of words) and economy (the fewest words without loss of clear expression and full thought). Lastly, they proofread the final copy.