If your roommate lends you something such as a book or CD, remember that you are not at liberty to lend it to anyone else. Always put borrowed CDs and tapes back in their cases. Never borrow anything without asking, even if you're sure your roommate won't mind. Mooching is often a source of friction. It is strongly recommended that you never ask your roommate to lend you money, buy things for you on his credit card, or cover your share of a joint bill.
Unpaid debts are a quick way to ruin a relationship.
It is highly recommended that you do not ask to borrow your roommate's clothes. Do not constantly ask your roommate to make change for the laundry. If he does make change for you remember to replace his coins the next day. He was probably saving them for himself. Make an agreement at the beginning of the year that if either of you does something the other finds disturbing, that you will tell each other.