It can start as simple as asking them. I used to work with a teacher who kept a stack of blue and yellow cards next to the homework basket. As students turned in their homework, they would select a blue card if they were feeling down and a yellow card if they were feeling positive. They would place their cards on their desk as they did morning work. Throughout the day, the teacher would make sure that she was able to check in with all of the blue cards to see what was going on with them. She even made time to celebrate with her yellow cards. It was simple and easy to maintain but it sent a strong message to your students that she cared about what was going on with them.
It's a simple idea, and sometimes those are best. If you're interested, I've created the clip chart for you in my TPT store. It includes 3 different color schemes, number tags, and editable name tags for clips. Just in case you've already posted your amazing MAP It Out wall, I made sure to use a complimentary color scheme.