Tell them to use a notebook to jot down experiences. Guide them in using correct grammar. Have them proof check their work misspelled words and clarity. Some writers say choosing among topics such experimenting and brainstorming is the best way to learn how to write. These exercises are looked upon as warm ups or in other words a rehearsal to prepare us for learning to write.
Calkins believes that writing has to become a part of the daily routine.
My experience with writing began with simple sentences. Overtime I have progressed to writing compound and complex sentences. After many years of writing, I have developed the skills to effectively communicate through writing. Writing has become a part of my life and everyday routine. In his book Calkins list the characteristics of good teaching.