Personally I like to commend based on any of or a combination of the following:

- Attitude (bad ones get you a big ol' goose-egg!)
- Communcation (social, or otherwise, anything to make repeat content more enjoyable)
- Performance (if you clearly excel at your role, I'll commend)
- Assistance (if you make a suggestion to another player who appears to be struggling, and do so in a constructive and polite manner, gj!)

I don't like when players assign commendations based on class because the DPS always get the short end of the stick. I've played only as a DPS in the DF since commendations were released and I have like... 120 total lol, people just hate on DPS for some reason, especially BLMs. I guess people just think we all sit in the back and do nothing, and all those fireworks are just set off by default :S

For the record, I always say hello, say gj and ty when we win, and also if someone needs help/explanation, I'm happy to do it if I understand their role in the duty well enough. That seems more like common courtesy to me more than something to do for a commendation lol