So, you've decided on a writing style and skills to practice.  Super! You have administered a writing assignment.  Terrific!  What's next?
The next step is to have the student read his work and look for ways to improve or revise what he has written.  Anyone can improve something when it comes to writing. Now this can be done the same day, but I suggest you wait a day or two.  Allow the writer to look at the work with "fresh eyes" after having put it down a day or two.   
For years I have taught students to S.T.A.R their papers. Someone had shared this with me a long time back, and it still works wonderfully well.  
S - substitute a dull word for a better one
T - take out words that aren't necessary and make the writing "wordy"
A - add in more description or detail, perhaps better vocabulary
R - rearrange any part that might be better suited before or after its placement
This is also a good time to start dating the progress on a Portfolio Record which should be kept in the Writing Portfolio.  Prentice-Hall has a great one. 
www.teachervision.com/creative-writing/portfolio-record?downloadpdf=print

Fantastic!  You have decided to create a valuable tool to help grow your young writer into a stronger young writer.  
Step one was to get a three ring binder and dividers labeled with each writing style.  (Simple definitions provided for your knowledge.)

• narrative - telling a story: non-fiction or fiction
• expository - explaining/informing on a topic or subject
• descriptive - visualizing characters, events, or places
• persuasive - convincing with reasons, arguments and justification

Personally, I like the dividers that have the tab AND a pocket.  
It is now time to collect your first writing sample.  Of course, you can assign any writing of your choice, but since this is your "Baseline Sample", you want it to be written with minimal help from you.   
Before you assign a writing task, you must decide on the beneficial writing skills needed for your child.   
You may want to refer to your child's grade level standards for direction with that. 
For example, I'm having my fourth graders working on CCSS 4.4 in writing: "Produce clear and coherent writing in which the development and organization are appropriate to task, purpose, and audience."  We are also incorporating CCSS 4.3, 4.8 and 4.10 as each writer will work on a narrative with a relevant experience adding revision and reflection of his or her work along the way.  
So, the writers will be asked to write about  a "Summer Moment" after filling a whole page with pictures and words of places, things, and people. From that pre-writing activity, the students will choose the one moment that meant the most this summer. The only directions given them will be to write and describe that moment to the best of their ability.  That's our starting point.  
Use a writing prompt that suits your child and supports the style and purpose you need to instruct.  There is much to be found at www.k12reader.com, but one specific page worth visiting is: Expositive Writing Prompts - All Grades

Are you teaching writing?  You probably have many questions.  Here is a common one.  
Is there much of a difference between a folder full of our writing assignments and a "Writing Portfolio"?  Absolutely.  A folder, without purpose, is just an organizing tool keeping items in place.  A portfolio should create an image of an ongoing collection of writing samples intended to record the process of your child's writing over time.  
Collecting work is not the same as assessing work.  Folders collect.  Portfolios assess.  
Writing Portfolios Should:

• show the development of your young writer over time
• aid you, the teacher, in further instruction and direction
• act as communication (written and verbal) between your young writer and you
• provide learning moments and tools for your young writer

This year, begin with a 3-ring-binder and some pocket dividers.  Label the dividers with each style of writing:  narrative, expository, descriptive, persuasive. 

All moms worry.  Right?  Well, in my experience, homeschool moms worry even more.  Through the years, I have heard many of their trepidations.  If you homeschool, or are considering it, let me ease your mind on three common angsts and tell you what should consume your time instead.  
1.  Homeschool parents worry about their children's socialization skills.  Please don't.   Heidi St. John http://heidistjohn.com/ said it best when asked if she worried about her children's socialization.  Her response was something like, "Heck, yes!  That was why I pulled them OUT of the public classroom!!!"  Truly, that is funny, right?  Good socialization skills come from the practice of being social, talking with others, building friendships, learning to compromise, etc.  These skills can happen anywhere, and not only in a classroom with 30+ other students.  I LOVE homeschooled kids.  They actually look me in the eye when we talk!  Their parents taught them that.  
2.  Many moms panic and question if they "taught enough" on a particular day.  Once when I arrived to meet with a family, the mother opened the door and quickly apologized to me saying it wasn't a very productive learning day.  When I asked what she meant, she explained that they got sidetracked.  While coloring her assigned phonics page, her kindergartener had asked if crayons would melt in the sun.  The mom responded with, "Let's see.  What do you think?"  And, outside they went.  They put some crayons in the sun and then decided to bake some in the oven.  Then the daughter wanted to put them in various shaped tins; like circles and hearts, to see if they would take on the form of the pan.  I simply smiled and congratulated her.  It is not every day that a student is so engaged in learning that science lessons can go from 20 minutes to 2 1/2 hours! A school day does not have to look like it did for us --- sitting in a chair for hours at a time. Your hours of learning in a day can happen anytime, anywhere, all day long.       
3.  What if I can't make it the whole 12 years?  Or, even one year!?  These are common concerns.  My advice --- just take it a week at a time, then a month, then a year.  If you stay with it longer, great.  With the right support, I think you can!  If, however, you find it isn't working, you are not a failure (and neither is your child).  No one knows if she can do it until she tries.  That is the journey.   
So, what is worth worrying about?  You are.  A homeschool mom needs to take the time to think about why she is making this choice for her child and family.  She needs to talk to other moms who are being successful.  She needs to find balance, and supportive people (friends and family) are a must!  She needs to take care of herself: spiritually, physically, and emotionally.  Your strength in all of these areas will make all the difference.  I promise. 
Once you have taken care of YOU, you will be far more confident, prepared, and encouraged to do the most important job of your life.  

Why can planning our language arts lessons be so time consuming?  Well, for one, LA includes so many subcategories.  We have reading, AND writing, AND spelling, AND grammar.  A good handful of homeschooling parents would feel pretty good if their child read for 30 minutes, practiced some new spelling words, and produced beautiful cursive on page 32 of the handwriting book.   Look at ALL that language practice, right?  Wrong.  Eventually, the parent-teacher is going to realize a rather large component is missing:  the structured writing practice. 
A good handful of homeschooling parents would feel pretty good if their child read for 30 minutes on a given day, practiced some new spelling words on Spelling City, and produced beautiful cursive on page 32 of the handwriting book.   Look at ALL that language practice, right?  Well, right and wrong.  Where is the detailed, structured, organized, descriptive, and focused writing?
Eventually, the parent-teacher is going to realize a rather large component is indeed missing:  the structured writing practice.  And, if a time crunch is approaching, it might be tempting to place that dreaded clean, white, lined paper in front of the student and announce, "Today you are going to write one paragraph about the book you just finished."  Some kids flourish when given such a task; however, many more simply stare at the blank canvas---not even sure where to begin.  Can you relate?
As a child, I only needed a few of those experiences before I hated writing assignments. I just didn't know what was expected of me: "How long should this "paragraph" be? How do I even start a paragraph?  And, how many times may I use the word "very"?"
The key to producing successful, accomplished, and happy writers is to give them the structure they need to be successful, accomplished, and happy!  Take the time to learn the four main styles of writing.  Provide clear and direct instruction.  Give students time to practice the style.  Establish consistent writing methods to ensure quality writing is being produced.  
If that sounds like a lot to do, well, it is.  It can be difficult, too, when you are planning for all of the other core subjects and electives.  So, let me help.  Relax, I have done the work for you, and I will continue to design and add more products regularly.