Don't do it
You should not litter the gym.
You should not wear slippers in the gym.
You should not fight in the gym.
You shouldn't talk too loudly in the gym.
You shouldn't stay too long.
You should not wear inappropriate shoes.
Things to do
You should exercise hard.
You should wear inappropriate clothing.
You should bring the tools back in place.
You should not talk on the phone while practicing.