Best way to get a commendation (aside from playing a tank) is to stand out. I am not talking about playing better then the rest, but standing out in a social away. People join a group and most of the time its only Hi, Hello, Good morning/afternoon/evening, salute and they end it with a Bye or a Goodbye.

When you join a group, ask people how they are, when you see people raging at each other, try and defuse the situation. For me whenever I see someone making a fun joke (nothing racist,sexist, hurtful to the player etc.) I tend to remember them alot more then the others and they often get a commendation from me.

So stand out in a good way.