What can we learn from Thoreau about writing?
Great things can come from a journal ...
Thoreau Reader:  Home - Teaching
"What are you doing now?" he asked, "Do you keep a journal?" — So I make my first entry to-day. 
(Thoreau's first journal entry of October 22, 1837, thought to be a response to a remark by Emerson) 
Following Thoreau's examples:
One very serious, and one less serious...
Crafting an abolitionist speech from journal entries, Thoreau Transforms His Journal into “Slavery in Massachusetts” - with an appendix that shows exactly where Thoreau edited his original, and what he left out, with a link to the final result. - Dr. Sandra Petrulionis
Preserving the Stories of Concord: Mad Dogs, Mud Turtles and Escaped Pigs: Thoreau as Storyteller in the Journal - "Thoreau had an author’s intuitive sense for good copy, deliberately choosing themes based on what he called “homely every-day phenomena and adventures" - Dr. Sandra Petrulionis 
Harvesting from your journal:
Using Thoreau's methods...
Using Thoreau's techniques: Robin Vaupel's  "Connecting with Thoreau" is a middle school lesson plan for journal writing, based on Thoreau's work. "Following Thoreau's example ... use journal writing as a way to bring out your own ideas and develop your writing." 
Thoreau as a Model for Nature Writing: Thoreau’s journal became his most important writer's tool - "Nature writing is born of love, respect, and awe. It finds its subject during days of close observation of the natural world. It finds its voice in the relationship with nature developed during those days. - Ron Harton
"His journal ... does not consist of mere scraps, hasty memoranda, and jottings-down, like Hawthorne’s note-book, and like the blotter most literary men keep, but of finished work — blocks carefully quarried, and trimmed, and faced, at least with a plumb spot upon each, to be used or rejected in the construction of future works." - John Burroughs
Thoreau Reader:  Home - Teaching