I'm not sure how old your child is, but IEW (Institute for Excellence in Writing) worked wonders with our children.   We homeschool, so this may or may not be a help for you.  It's strictly a writing curriculum that is not designed to place impact on grammar, spelling, etc...  It's designed to teach children how to write in a clear, concise way that allows them to take their thoughts and put them on paper.  Can't say enough good things about it!

I feel your pain!  Kids have a negative connotation with writing thanks to testing and essay writing.  I don't know how old your child is or if the essay is from a prompt or from a content area assignment. So here are some ways to to motivate kids to write by letting them do what real writers do!  To help them tap into their inner author you can try the following:
• let them write about what they are interested in
• let them pick their topics, let them brainstorm and draft in a writer's notebook for a week or so and then have them go back into that notebook to pick a piece he/she wants to spend time making better
• don't dwell on drafts being perfect, instead celebrate ideas, word choice and details that paint pictures in readers' minds.  Final attention to spelling and conventions can come when the final piece is ready to be written
• let kids decide the form of the writing they want to develop, whether they want to write an essay, or a story, or a poem

As students gain confidence and learn that they have control over their words and ideas, they may not dread the dreadful essay, or at least they will realize they can get through it!

Hope this helps!

If you are working on writing essays or paragraphs with your child, there is a great software package called Kidspiration at www.donjohnston.com that is a fun way to teach these skills.

Do a rough outline of your ideas in a notebook you can carry around and then whenever you get an idea, just add it in the appropriate place on the outline and eventually your essay will be practically all finished. Good luck! You still have a lot of time so don't waste it.

Maximum motivate them to read books or anything as much as you can. Reading will develop deep thinking and it will give a wide knowledge about something. Through reading we can get some great author's writing style, how much you read that much you can get the best. :)