A few things that come into mind that I've seen of late.
Considerations to Airmanship and Discipline.
Airmanship can be learned from others and gained by experience. Airmanship is a broad term used to define a series of positive behaviours/abilities and of an awareness of the environment that we operate in.
To summarise: Use your head and don't be selfish.
Basic rookie errors:
Propwash - Have a think about where you're pointing the tail of your aircraft and how much power you're using. You wont make many friends with engineers if you go blasting dust through their hangar or blowing over cowling etc, while they have the aircraft apart. Your mates wont be happy when you blow their doors shut on them while they're trying to load freight etc.
Doors/Windows - Keep these shut while you aren't using them. Here is one for you to picture: Your hamfisted new work college, just checked to line on a C210, does a 180 tail to tail with you at 1700RPM while you're loading a person who has a stiff leg into the aircraft and not guarding the door. The door swings open, catches the prop wash and subsequently breaks of at the hinges. Embarrassment, a loss of an aircraft door and a please explain from the boss are going to be the consequences of the day. Personally I've seen the result of a 210 who's doors were left open overnight, have a Conquest start behind it and tear the doors clean off at the hinges on two separate occasions.
Be especially cautious of low winged aircraft and open storm windows in the wet. Moldy carpets and wet bums aren't much fun.
Parking: A daily struggle due to the lack of room, complicates parking. I see plenty of rookies parking directly behind aircraft to get 20m closer to the gate and blocking that aircraft in the designated parking area for the duration of their wait.
Aircraft Washing: Fairly straight forward. Nothing looks better than clean tyre rims and oleo struts. Avoid water etc around the static ports and pitot tubes.
Final walk arounds: Once your aircraft is loaded, take 30 seconds to do a quick lap of the aircraft. Make sure oil caps/doors are secure, baggage lockers are shut and locked, fuel caps are on, chocks are out, pitot cover is off and that dreaded passenger seatbelt is not hanging out the door. All these are easily missed and consequences vary from embarrassing yourself to potentially an off field landing.
If it's any advice that you take from this post, I would suggest that it's the "final walk arounds" as I'd be willing to bet the vast majority of us have been caught by at least one of these.
Fly safe out there.