Frist, what are the group jobs? 
A research group can only function if all its members strive to fulfill their duties. This means you are in the group not just for conducting experiments, you are also supposed to maintain the tidiness of benches, the function of instruments, and a good research environment in general.

Second, what are my group jobs?
Click here.

Third, any guidelines? 
If you are in charge of a certain instrument, you set the rules and should enforce it. If there is anything that you consider inappropriate, you should let the corresponding group member know of. You can also discard any samples that you are not aware of, since their owners do not care about these samples anyway. It is fine if you feel uncomfortable to enforce it, but do not complain when Chong is angry at you or asks you to tidy things up yourself. If you obviates the duties after a few warnings, Chong may take further actions.