c) Do not call a roommate "petty" for being angry if you break something inexpensive, but sentimental and irreplaceable.
And as an follow-on:
If you agree to share the use of items you own personally, from dishes, to books and DVDs, to furniture, accept that normal wear and tear is inevitable, and accidents happen. You can expect your roommates to be careful, but you can't make them promise, for example, that they will never trip and drop a glass.
If something is either extremely valuable, irreplaceable, or of deep sentimental value, it is better kept in your private area to protect it, rather than in the common areas.
And as general notes:
Renting a room or having roommates is a legal agreement, not just a social one. Therefore, there are things you need to have in writing, in a lease, rather than either assuming that other people have the same idea you are, or that they will follow your expectations. This is for all the roommates and the landlord, and includes
Rent: how much, when and how will it be paid.
Utilities: what are they, and how will they be paid/split.
Leasing: duration of the lease, renewal, how to give notice, how long in advance, subletting, who can have keys
Behaviour: Non-smoking, non-drinking, vegetarian, no recreational drugs should be settled in advance
Other people: policy on entertaining, overnight guests, long term guests and SOs, as well as what happens if someone wants to move an SO in.
And finally, the biggest thing is to not assume that other people do things the way you do, or have the same ideas. Ask them. Discuss things before moving in, so you have an idea about whether your style of living and boundaries match well before moving in. Odd Couple scenarios may look well on TV, but aren't fun to live in.