Don't play engineering, atmos, janitor or any other jobs so crucial for the station's upkeep that it is taken for granted. Sure, you can be a great atmos tech, but since it dosen't directly affect them, they don't get karma directly (unlike someone in medical, who gets karma up the arse just for doing their job as it involves interacting with people), and most of the time they aren't noticed. A good engineer or atmos tech doesn't get noticed. A great engineer builds an autism fort that makes all the other Engineers applaud him. They only time when Engineers and Atmos techs are really noticed (and would get karma) is if something is going badly wrong, either through their incompetence or bad things happening. You can bet on everyone blaming the Engineers and not on, y'know the traitor screaming over comms about their evil plan.
In short, don't play for karma, play for fun, and you'll earn more karma (or won't if you play engineering).