On some programming days, I write "I can help with (feature being learned)" on the board. Students can add their names when they have mastered the feature and are comfortable helping others. This has encouraged students to help each other. My first semester students did that well. I hope it works as well this semester!
All of our freshmen complete a short unit on teaming. It includes managing team conflict, leadership styles, etc. I'm sure that has helped as well.