Do apple seeds dream happily of growing up to be a tree?

How many little fish might see the stone I throw into the sea?
These are questions Marcus Pfister asks in his simple picture book Questions, Questions. Since we know curious children are an endless collection of questions, let's record some of them. Give students a sheet of paper with the title "Questions, Questions."  When they ask questions throughout the day, direct them to the paper, where they can write them. Add the questions, one after another, until students have a healthy list.

If your students are young, they can write and illustrate their best questions in a mini-book. Assignment accomplished.  If they are older, you can expand this assignment, having them follow the example of Pfister whose questions are couplets 14-16 syllables long. Now they will have to figure out how to revise their questions, making them sound poetic with rhythm and rhyme.

If your students do this assignment, please include their best questions in the comments!
My daughter's Advanced Placement teacher used exercises from Voice Lessons to help her students develop their writing voices.

Each lesson is one page, including a quotation from literature which illustrates one of five categories--diction, detail, imagery, syntax, and tone--a couple of questions to lead students to examine the text closely, and a short assignment for application. In less than twenty minutes per lesson, students can learn to read as writers, appreciating what authors do well and practicing it in their own writing.
Discovering Voice is similar to Voice Lessons, except that it's intended for a slightly younger crowd. The quotations come from less advanced literature, and a sixth category--figurative language--is added. I used this resource with my 9th and 10th grade students last year, many of whom hadn't been in a prior formal writing class.
Two recommendations:
With either book, discuss the quotations, so that students have the privilege of both sharing and hearing insights.

View the exercises as tools to help students unveil the craft behind the words, not as worksheets to be completed halfheartedly.
Five Minute Friday kids edition
I went on an unplanned online journey yesterday and ended up at Lisa-Jo Baker's site, where I learned about Five Minute Friday. Each Friday, Lisa-Jo posts a word, her readers sit and write for five minutes about that word without editing or self-critiquing (at least that's the idea), they link their results, and they encourage the person who linked before them.  One of Lisa-Jo's readers, a mom at Desperate Homeschoolers, has regularly participated in Five Minute Friday , inviting her eight-, six-, and two-year-old daughters to join her, writing or drawing as they are able. Until recently, she has linked their work with hers.  Now it has a special spot, and your children's writing can be there, too, on the Five Minute Friday: Kids' Edition!

What a perfect way for moms and their children to write together with an achievable weekly goal and an audience.

Friday is coming! Cast the vision. Find some loose paper or start a writer's notebook. Sharpen the pencils. Ready...Set...Write!

I like using Harvey S. Wiener's idea from Any Child Can Write (68-69) to help young or reluctant writers transform a simple sentence. 

Begin with a simple sentence. In his example, Wiener uses "A child played."

Describe the Child: A child with brown eyes played.

Tell When: A child with brown eyes played one crisp winter morning.

Name a Sound: Giggling, a child with brown eyes played one crisp winter morning.

Tell Where: Giggling in front of his house, a child with brown eyes played one crisp winter morning.

Use Other Specific Words: Giggling in front of his house, a boy with brown eyes jumped up and down one crisp winter morning.

Once the student is happy with his improved sentence, ask him to rearrange it several times.

  • A boy with brown eyes jumped up and down one crisp winter morning, giggling in front of his house.
  • A boy with brown eyes, giggling in front of his house, jumped up and down one crisp winter morning.
  • Jumping up and down one crisp winter morning, a boy with brown eyes giggled in front of his house.
  • Giggling, a boy with brown eyes  jumped up and down in front of his house one crisp winter morning.
  • In front of his house, a giggling boy with brown eyes jumped up and down one crisp winter morning.

Possible discussion cues:
    Have the student rank his sentences from his most favorite one to his least favorite one.
    Notice how the punctuation changes from one sentence to another.
    Discuss what happens to the sentence when the subject is not mentioned immediately.

Other simple sentences from Wiener (69):
A man worked.
The book fell.
A tree moved.
The car drove away.
A cloud passed by.
A woman danced.
A girl ran.
The baby cried.
The radio played.
She pulled him.