I'm thinking about ditching my membership, but that's another post.
For the moment...things that are not appropriate:
Wearing pants so low I can see your underwear on the treadmill. As in the waist band AND the top 2 inches of them. Continuing to wear them so low that every time we cross paths lifting, I again see them. Sigh (side note, this could also have been solved by wearing an appropriately long shirt).
Talking on your cell. If the call is that important, get off the machine. You're not working hard enough anyway.
Not wearing a shirt. It is NOT that hot in the gym. If its 90 outside and you're running outside and feel ok about it, sure, whatever. Not in the gym.
Sitting on a weight machine chatting. For like 10 min. reps, Rest appropriately, repeat as desired, off.