While our crime rate, petty or otherwise, is very low, some theft does occur. Our first piece of advice to new students is to leave irreplaceable items at home if at all possible. If you must have a particular irreplaceable item with you, don't keep it in plain sight, and the fewer people who know you have it, the better. The next item that comes to mind is to mark your belongings so that if they are stolen and recovered by police, you can easily identify them. Most petty theft is opportunistic in nature.
Someone sees something sitting around, picks it up, and takes off with it.
So, protect your stuff as well as you can, but be prepared to give the information needed if it is taken. Call OSS at 6617. Call your RA on duty. If that fails, call OSS at 6617. Call the Student Center at 6786.