During the day on weekends I am usually doing some sort of community service activity through the Community Service Center, whether it be hanging out with my Little Sib via the Siblings program, or performing a play with Children's Theatre. Sundays are my homework days. On the weekend nights I often find myself going to some sort of event - a comedy show (like by BU's premier sketch comedy group Slow Children at Play), a play, or a concert, and usually hanging with friends after, whether it be an apartment party of just hanging around at Sunset for nachos.
There are always all campus social events on weekends, things like dance shows, theatre performances, dance parties. These events are more prevalent in the beginning of the semester as a way to get everyone adapted to being back on campus or on campus for the first time. Then you always have the off campus parties, you will always be able to find a party. You can also explore Boston, no matter what direction you go in there is an interesting place to see.
A typical weekend varies. When you are fresh/soph it tends to be going out with friends to dinner and then possibly to a friend's house for a house party or go see a movie, etc. As you get older more of your friends will go out to bars, clubs, or other social scenes. It will depend on your friends and what you are trying to do, but there is always something to do on the weekend.
A typical weekend for me consists of performing with my a cappella group, seeing my friends in their on-campus performances and events, and then maybe going out to dinner somewhere in the city. It's so easy to get to different parts of Boston so it's great that there's so much to explore and you're never stuck doing the same thing every weekend.
In college, a lot of your night-life weekend fun will depend on if you are legal to drink. ***I am NOT saying that drinking is the only fun you can have*** I AM saying that being under 21 can somewhat limit your fun, as many concerts sell alcohol and therefore do not allow underage people. Also, all the clubs in Boston are 21+ for the same reason - if a venue sells alcohol, they aren't allowed to have underage youth. So, chances are you won't be able to go to a cool jazz lounge or out for a night at the clubs. There are exceptions of course - Cambridge doesn't have quite the same rule I don't think. Places like the Middle East and TT the Bears often have 18+ concerts of local musicians. Big concert names are usually all ages. Also look in Allston, right past BU West. Sometimes the Paradise Lounge, Great Scotts, and the Brighton Music Hall have 18+ events. Usually there are college night 'club' styled dances at some halls on weeknights. It can be a good way to get off campus. Other ways to spend your weekend nights include just hanging out with friends, shopping, going out to eat etc. There are plenty of cool places to just chill out. Once you are 21, the adult nightlife options open up immensely. There are PLENTY of clubs and bars and pubs to go to, all ranging in price. If you get on a guest-list for a club girls can often get in free/guys a discount before a certain time. However, be careful - it still is a city, and you have to be responsible for yourself. ALWAYS stay with a buddy. Also, the T closes before 1am, and clubs are only open til 2. So you will need to pay for a cab, and if you have ANY hope of getting said cab, you better leave the club at 1:30 am. During the days time it is MUCH more flexible. The city has TONS to do if you learn how to look. Using the Boston University calendar can help you find all sorts or shows, concerts, activities etc on campus and can be a good resource to find things to do if you don't want to go far. For the city, I always check out the Phoenix paper for art events (free!) and boston.com/calendar for all the best events. Also, the city of Boston's website has a calendar with city-wide events which can be helpful. Don't forget to look in other easy-to-get-to areas like Allston, Cambridge, Brookline and Brighton. Plus, BU students get in free to the Museum of Fine Arts which is full of cool artifacts and artwork, as well as the Institute of Contemporary Art if you are interested. During the baseball season, you can get student rush tickets if you stake out - plus Fenway is literally RIGHT next to BU. If you want a nice walk, hanging out along the Charles River on the bike path is great especially y in spring and summer. Don't forget - you have an ENTIRE city to explore! The North End, South End, Faneuil Hall area, Back Bay etc. All of them have VERY distinctive qualities and are all different. There is ALWAYS something going on - you just need to be proactive in looking to find it so you don't miss out!