If I'm awake at 2am on a Tuesday and I am not studying, I am probably having a dance party with my roommates. The roommates I currently have as a senior I met because they were on my residence hall floor my freshman year. All of us left our doors open, and residents still do, and I think that aspect allows more people to meet and make friends. When we are asked to give prospective students advice, you will always hear one or two people tell the students to leave their doors open. I know the last time I spoke on a student panel (this takes place at large visit days or recruitment efforts where audience members have the chance to ask current students any question), my advice to students was to leave their door open, pop a bag of popcorn (but don't burn it because then you'll lose friends) and the smell will attract people to your room!
I think most of the questions in this section I answered in the very first box i filled out. But there is so much to do on campus. If you don't want to drink, Campus Activities Board is hosting a free concert or free casino game night for you to attend. Every so often the Field House hosts night games and leaves everything open late.
To be honest, I can not say what the most popular groups or organizations on campus are. Everyone is involved in so many different things. The larger groups are the ones you see more often on campus: STAT - Students Today, Alumni Tomorrow, they're always giving away free stuff and trying to get students to become members. When Student Government elections come around those different parties will be out campaigning on campus. Other than that, I don't see one group "dominating" campus. The Greek life is present, but not overbearing. I am not a part of the Greek system and I am very happy with how my four years have turned out. I did attempt informal rush, but ended up not liking and felt like it was too expensive.
The student group that I am involved with is STAR - Students To Assist Recruitment. We are a volunteer organization comprised of about 160 members that, as a whole, donates thousands of hours of our time to recruiting potential Hawkeyes. I currently serve as President, a position I would've never imagined holding when I was in high school, or even when I first joined the organization. The group has allowed me to grow as a leader while doing what I love: talking about Iowa and promoting Iowa to prospective students and their families. I talk more about this student organization on job interviews than any sort of work or professional experience I've had.