There is quite a bit of underage drinking, but RAs, hall directors, and campus security make sure that things stay safe. The police do not really come on campus unless they are called. If students are smart, they can have a fun time without getting caught, but it's often best to play by the rules and be smart about your choices. Overall, people would say that campus is not that strict, although when it comes to things like grades and plagiarism, the administration really cracks down and takes those situations seriously.
As for attendance, it depends somewhat on the professor. Most will take attendance and calculate it into your grade. Others say you can do what you want and are responsible for making up what you miss and staying on top of things. Still, some professors are very strict and do not tolerate tardiness. Plus, classes are small enough that professors know when you aren't there, whether they take attendance or not. And, if you do choose to skip class, look out because it isn't uncommon to bump into your professor later that day, which can lead to awkward conversations.