I main paladin. My personal Commendation guidelines that I use whenever I dish out these goodies:

Did one dps use LB appropriately in every boss fight it was available? Instant commendation. Top priority (its my biggest pet peeve when dps don't LB appropriately or let it just go unused, so I really like to reward people who use it correctly).

Did the tank pull appropriately sized groups for our item levels and party composition? Instant commendation (for when I'm not tanking).

Did the healer dps when party hp was full? Instant commendation.

Did the tank pull too much without warning yet the healer is able to keep him alive? Instant commendation (for the healer).

Otherwise, no one gets commendations. If both healer and tank are good, its a matter of who I like more based on who talks.