Congrats! I'm not strictly a developer, but I do a lot of development as a Geospatial Engineer and I'm not a manager, but I'm in on management discussions all of the time. As far as corporate culture and such goes, I've got a few tips:
-Take notes. Have a notebook and pencil with you at all times.
-Don't complain about corporate nonsense like the time sheet or filling out forms. They know it sucks.
-Ask good questions. Don't just sit and listen and then ask for a recap. I've literally had someone say "Can you go over all that again?". No.
-Don't play around on your phone, put your feet up, or sleep during meetings. Yes, I've seen all of these.
-If you need a sick day, just take it off. Don't say you got drunk and a hooker broke your arm and stole your wallet. Just say you're not coming in.
-Remember that you don't know everything. A degree is a great thing, but each of your classes works out to maybe 80 hours of lecture time plus studying. That's two weeks in the real world. Your coworkers have probably been neck deep in whatever project for months if not years. Have an appreciation for how much you don't know.
-Be respectful of the culture. Some places are laid back, some really tight assed. Just hang out and do a good job. Be friendly and helpful. Once your coworkers know that you're not going to wreck the office vibe, they'll warm up to you.
Good luck!