Writing Next explains 11 research-based practices that make a difference for student achievement:
Writing strategies: Explicitly teach students strategies for planning, revising, and editing their written products. This may involve teaching general processes (e.g., brainstorming or editing) or more specific elements, such as steps for writing a persuasive essay. In either case, we recommend that teachers model the strategy, provide assistance as students practice using the strategy on their own, and allow for independent practice with the strategy once they have learned it.
Summarizing text: Explicitly teach students procedures for summarizing what they read. Summarization allows students to practice concise, clear writing to convey an accurate message of the main ideas in a text. Teaching summary writing can involve explicit strategies for producing effective summaries or gradual fading of models of a good summary as students become more proficient with the skill.
Collaborative writing: Allow students to work together to plan, write, edit, and revise their writing. We recommend that teachers provide a structure for cooperative writing and explicit expectations for individual performance within their cooperative groups or partnerships. For example, if the class is working on using descriptive adjectives in their compositions, one student could be assigned to review another’s writing. He or she could provide positive feedback, noting several instances of using descriptive vocabulary, and provide constructive feedback, identifying several sentences that could be enhanced with additional adjectives. After this, the students could switch roles and repeat the process.
Goals: Set specific goals for the writing assignments that students are to complete. The goals can be established by the teacher or created by the class themselves, with review from the teacher to ensure they are appropriate and attainable. Goals can include (but are not limited to) adding more ideas to a paper or including specific elements of a writing genre (e.g., in an opinion essay include at least three reasons supporting your belief). Setting specific product goals can foster motivation, and teachers can continue to motivate students by providing reinforcement when they reach their goals.
Word processing: Allow students to use a computer for completing written tasks. With a computer, text can be added, deleted, and moved easily. Furthermore, students can access tools, such as spell check, to enhance their written compositions. As with any technology, teachers should provide guidance on proper use of the computer and any relevant software before students use the computer to compose independently.
Sentence combining: Explicitly teach students to write more complex and sophisticated sentences. Sentence combining involves teacher modeling of how to combine two or more related sentences to create a more complex one. Students should be encouraged to apply the sentence construction skills as they write or revise.
Process writing: Implement flexible, but practical classroom routines that provide students with extended opportunities for practicing the cycle of planning, writing, and reviewing their compositions. The process approach also involves: writing for authentic audiences, personal responsibility for written work, student-to-student interactions throughout the writing process, and self-evaluation of writing.
Inquiry: Set writing assignments that require use of inquiry skills. Successful inquiry activities include establishing a clear goal for writing (e.g., write a story about conflict in the playground), examination of concrete data using specific strategies (e.g., observation of students arguing in the playground and recording their reactions), and translation of what was learned into one or more compositions.
Prewriting: Engage students in activities prior to writing that help them produce and organize their ideas. Prewriting can involve tasks that encourage students to access what they already know, do research about a topic they are not familiar with, or arrange their ideas visually (e.g., graphic organizer) before writing.
Models: Provide students with good models of the type of writing they are expected to produce. Teachers should analyze the models with their class, encouraging students to imitate in their own writing the critical and effective elements shown in the models.
--Evidence-based practices for teaching writing, Gillespie and Graham
To see a summary, read this on Adolescent Literacy.
ADDITIONAL RESOURCES:
Zemelman, Daniels, and Hyde have updated their book Best Practice. Scroll to page 132 to find what they have to say about the best practices for teaching writing: Sample from Best Practice
Here's another document listing best practices. For those who believe in formulaic writing, be sure to read the section called "Caveats Regarding Two Teaching Practices" on the next to last page: Best Practices for Teaching Writing
In this excerpt from her book on best practices, Laura Robb shows how writing the essay can be exhilarating!
NCTE's position statement on writing
Roy Peter Clark's blog contains smart, important tips for writing from a writer.