The most popular groups on campus are theater/vocal groups. Students for Israeli-Palestinian Peace, a group I was involved with, threw events that were pretty popular, but the most popular events are dances and readings. Athletic events rarely gain popularity, but guest speakers and theater are frequently attended. The dating scene is practically non-existant--sorry ladies, you're most likely not going to find your man at SLC. Most women find a guy they like, and once the guy realizes he's male at SLC, he discovers he has his pick of the litter. The male/female ratio really works in their favor, and it makes it really hard for us. The relationships I've been in have been with people I've met off campus--it's all just networking, so don't worry, you'll meet someone.
If I'm awake at 2am on a Tuesday, I'm studying. Sometimes I'll be awake at 2am on a Friday night studying. There's a lot of work, but I mean, it's manageable, and it's whatever you're interested in so it's more fun than normal busy work.
Traditions, again, are usually dances. Our craziest, most infamous dance was the "coming out dance," a dance at the end of our coming out week, a celebratory week for LGBT students, and anyone who wanted to express their sexuality. It was cancelled after my first year because too many people were sent to the hospital for alcohol poisoning. It was unlike any other dance, and I doubt anyone will be able to replicate how amazing it was. So it was really a shame that people got so out of control with it that they had to be hospitalized--it's the reason that our "sleeze ball" got cancelled too, because some people like to ruin things for everyone else. Please, please, if you do decide to go to SLC, don't be one of those people.
At SLC, I would party maybe once or twice a week, on the weekends. That was pretty much the norm, I think. Some people partied a little more, some people less, like any place. If you really want to find a party, you'll find one, or you'll make one happen, it's not very hard to do. If not, there are always other things going on--concerts, readings, dances, etc. etc., the programming board works hard to create other alternatives to drinking and passing out.
Off campus, I usually either go to the local bar (an Irish pub, which is really fun) or to the diner down the road. There isn't a lot of activity in and around Bronxville, but NYC is a 20 minute metro-north train away (if you want to spend 12+ dollars round trip, including the train and the subway). People go to the city all the time on weekends, and there's endless amounts of things to do there.