I like to delegate responsibility to the student. I begin each semester by presenting the student with one of each of these passes. I give a total of 8 bathroom passes for a semester (however, only four at first because they "lose" them). If they don't use the passes, they become extra credit at the end of the semester.
I also give them four nurse/office passes, but I also have my own because they cannot go to the nurse without a pass.
Then, I discovered this "Pink Slip" idea somewhere and made my own. If the student does not have an assignment on the due date, s/he fills out one of the pink slips and I have it as a record and for a parent conference later.