Rule 1: If you are working only for part-time, do not release your MSN or other chat program’s email to your colleagues who are working closely with you.
Rule 2: If you are having holidays, let your colleagues know that you are going overseas even if you are not, so that none of them would bother you during the break you deserve.
Apart from these, think thrice before you start to portrait yourself to others. If you are going to be very helpful, your colleagues would most probably take you for granted; and you probably would take up more extra jobs, and mostly are invaluable.
Working life is tough. Students should cherish and enjoy their freedom before they start going out to work.