Place a set of cards in the pocket folder over each child's name card. This pocket chart will now serve as a mood indicator. When you have it created, sit down with the kids and explain what it's for. Encourage children to update their mood cards daily, or whenever their mood changes in the classroom.
What makes this activity a valuable tool for social skills and emotional intelligence is the follow up. Check the chart periodically throughout the day, whenever you convene for group time or gather the kids for transitions. Have them check the chart for any mood changes. If there are any, have a discussion about this. Ask the children if anyone noticed anything that happened, and ask the child if they'd like to share why their mood changed. (Don't press the issue if they'd rather not, and also give them the option of discussing it in private.) These discussions give you a chance to talk about things like how our actions effect the mood of others, what different things make kids sad or happy, and how to put ourselves in someone else's shoes to imagine what they are experiencing. Inevitably you'll have kids change their cards after conflicts in the class, and this provides a wonderful opportunity to discuss social skills or work on conflict resolution.
It's an excellent way to build empathy in children. One of the biggest barriers to overcome in building emotional intelligence is simply finding ways to talk about emotions in everyday life, since it's a topic that is rarely explored elsewhere. After a while, kids will begin to notice when someone's chart changed to the negative, and will take the initiative to try and comfort them on their own.