Divide each page in your notepad into two columns. One of these columns will be for the students' names, and the other will be for your comments.
Write the day's date at the top of the first blank page in your notepad before you make any observations. This will help you to keep your notes organized chronologically.
Place your notepad on an open, accessible place on your desk. If you do not usually carry a pen with you, also place a pen beside this pad. If you spend a lot of time away from your desk or want to make sure that you jot down your observations as you make them, then carry a notepad and pen with you, or have notepads placed throughout the classroom.
Observe your students while they are in the middle of an activity.
Take note of any activity that stands out to you. Perhaps a group of students is solving problems on their own, and not bringing questions about the assignment to you; make a note of this, along with the students' names. Or, perhaps a student is consistently disrupting his group whenever he is assigned to work with the same group of students.
Compile your anecdotal notes into a separate binder, or word document after class. Make sure that you organize them by date and by student. Then, when you need to write a comment about a student, you can refer to your collection of anecdotal notes.