Whether your students are familiar with writing in journals or not, this PowerPoint gives them your expectations. It includes visuals of what writing time looks like and doesn't look like. It includes the MAISA guidelines of using pen, being respectful, personalizing journals, using the journals only for writing, and including dates and titles with each entry.
In addition, I have included a portion about Brain Babble.
I have also included a slide of music guidelines if you like to play instrumental music during writing time. I love instrumental music because it is an auditory reminder that writing is happening even if they are late to class and exposes my students to classical music.