If the dungeon went smoothly order of general commendation:
1) If new player(bonus) , commend new player.
2) Commend if exceptionally engaged and friendly.
3) Commend Tank if on Healer and reverse. Commend other DPS if on DPS.
If anyone has a poor attitude, I'll move on to the next person on the list. Most partys start on 3, because no new players enter the dungeon, and no one usually talks, so you can't really gauge their attitude. That's how my commendation system works.