Write first and then edit
When you have freedom of thought and flow, you may be more creative in writing. So don't write and correct at the same time! First - write. Then - edit. You'll see better results.
Give yourself time
Be sure that if you write, you have still much time to read it many times and check spelling mistakes or some errors.
Quality over quantity
Write a little less but check if things you have written make sense.
Print your paper out
Not always you'll be able to see all mistakes on the screen. Seeing your ...