This is an effort rubric I created to explain effort to primary students. It is based on information presented in The Skillful Teacher by Jon Saphir. I have it hanging in my classroom next to the wall where I display student work.
It includes a simple poster explaining what makes up effort and a visual self-evaluation with three posters explaining what earns a smiley face, a straight face, and a frown. In addition, I recently added a self-evaluation form students can fill out at the conclusion of a project/assignment. They draw in the face (smile, straight, or frown) next to the areas of effort based on how they evaluate their own effort.