The best advice that can be given to incoming freshmen is don't drink, don't smoke. But if you are going to do it, be careful. Most students get caught with a beer, whether in the dorms or at a party, at least once in their college career, and the punishment just depends on who catches them. A lot of students get away with drinking in their dorms, while others don't dare for fear of their RA's wrath and a referral to campus judiciaries. The same goes for both police departments; it just depends on each situation. Usually, unless you're making a huge scene or are a danger to yourself, most cops will allow you to stagger home from a party or bar in peace. It's those people who are falling all over themselves, being loud, or relieving themselves in public that are going to be stopped by the police.
Whether you drink, or just want to light a candle in your dorm room, use common sense and good judgment. If you choose to drink in your dorm, don't make it obvious, and be respectful to the other people in your hall (i.e. loud music, breaking glass, and doing drunken cartwheels in the hallway will definitely get your RAs attention). When it comes to Court Street and the "fests," don't make yourself obvious to the cops. If you do happen to stumble and fall, just tell the officer you're on you're way home. It's always best to use the buddy system too-so the cops know your not in any danger. Just cooperate either way-being belligerent isn't going to get you anywhere except a trip to jail.