Graphic organizers are a great way to start the writing process. Providing students with a map of how writing can be outlined and then put into paragraphs takes the pressure off of staring at a blank page. I also think it is good to have a writing notebook, so that each written entry is dated and kept in order. This way students can see their progress.
Copy editing is essential. A first draft, followed by a second draft allows students to self correct and see their ideas presented in a professional, clean manner. This honors their writing, teaches spelling, grammar and punctuation in a meaningful context.
Finally, it is important for students to write every day. Writing prompts can help with this, but I think encouraging students to write their thoughts just exactly as they occur in their minds is also important. A good writer has a unique voice. Helping students find their voice is a great way to enhance self esteem.