I recognized very early on in my career how participation could be so subjective in nature. Therefore, I tried to make my participation/professionalism category of my grade as objective as possible. I use a five point scale for each class meeting. The students can earn a point for completing each of the following: being on time and not leaving early, prepared for class (have writing utensil, paper,etc), wearing student ID (which is required at our school and most careers), participating in class, having assignments completed that are not designated as graded assignments. If they are absent, then I can't see any of the subcategories. It results in a "0" for the day. I have never had a student dispute this grade with me. They actually tell me that they know what this part of the grade is in my class compared to some of the other instructors in our college.