I don't think you have much choice in any of those questions freshman year. Your commons is decided by which freshman seminar you get into and your dorm is, I think, somewhat related to who is in that class as well (I think they try to keep things grouped together somewhat in that regard). I believe you have to live in the same commons both freshman and sophomore year and then for juniors and seniors, it's strictly by lottery -- which would say to me that being in a particular commons has less to do with room choice than a lottery number. And like any lottery -- everyone has an equal chance of winning or losing (depending on how you look at it).
All of this being said, I really have no idea except that this is accurate but is only what I've gleaned from reading the website, the posts on here and a few other review type webpages (***** etc). <-- not sure they allow any references to other resources on here. But you get the point.