I generally commend people in the following order:

1 - Anyone who made things fun. Chatty, social, kept me entertained? You get the comm even if you weren't a great player.
2 - Anyone who was really good at their job.
3 - First timers and sprouts.
4 - DPS
5 - Healers
6 - Tanks
7 - Whoever didn't insta-leave before I could even click on a name.