We spent a lot more time than usual this year discussing and practicing and sharing ways to be a "good classmate". In fact, it became a mini PBL unit.
I did several read alouds of books with strong friendship/helping out messages, even for books that were not set in a classroom. That led to great discussions and Padlet comments connecting actions outside of a classroom to actions inside a classroom. For example, friends share a snack of cherries in the book Friends by Helme Heine, which is similar to classmates sharing markers in class.
Similarly, students read a couple books with a central friendship theme and talked about feelings of characters outside the classroom and then invented scenarios in the classroom that could cause a similar feeling. For example, after reading Ira Sleeps Over by Bernard Waber, students commented on Ira feeling embarrassed about bringing a teddy bear. Some of them suggested that a student might be embarrassed in class if they didn't know how to sound out a word.
We did a variety of activities related to working together. For the 1st 2 weeks before any partner or group activity we reviewed what it meant to work together. We came up with a list that included participate, listen, be respectful, compromise, follow directions, and help each other. In we did several iPad activities related to these rules. Students picked a rule, wrote it in the My Story app illustrated it, and wrote what would happen if the rule was not followed. They created skits demonstrating the rules, either using the camera app, Toontastic, or Puppet Pals (their choice). They also used the WeMap app to give specific examples of the rule to be sure that everyone understood exactly what that rule looked and sounded like.