In my classes I have a code of conduct as part of preparing them for the workforce. No foul language no racial or religious slurs etc. A exercise I found that works very well is verbally firing them and then asking them to explain the consequences of this action. For example cant pay rent,cant take girlfriend out cant pay for Christmas ,things that they have first hand knowledge of reminds them why they are in school and that petty differences when not handled correctly can adversely affect their lives. Once they see the affects they may have on their own lives they eventually star to fire each other which in turn helps me. It works since I started it the other instructors have started adapting it in their classes as well.