I'll commend a tank if he is geared and pulls big groups or new/not very geared but trying his hardest. When it comes to DPS, I'll commend them if they LB at the right times or give guidance to newbie group members. Once in awhile when I don't go as heals I'll commend the healers for putting up with my tanking. Lol. Sometimes I don't commend at all though. That happens when my group mates are all bad or being snarky.