I got mine legit. I tank and play a lot. That's all there is to it. Playing PvP is a pretty fast way to get commendations too by the way. Plus, now that parties can give out commendations to other players, if you're 1 person queuing into a group of 3 or 7 preformed (more likely to happen if you're a tank) then you're the only one they CAN commend, so it's like SCORE! But I had 600 or so commendations before the last patch so I never got that benefit. It should be even easier now and challenge log rewards people giving out commendations so...

You won't get that many if you do lots of preformed groups but if you queue for a lot of random things by yourself like I do (especially in a needed role) it's really pretty fast anyway. New rewards are a bit overdue in my opinion (that is if SE intends commendations to mean anything on an ongoing basis - they may not, it may have been just a one time deal).