I think this one has been discussed pretty well. Don't kiss up or start spouting off regulations like some idiots do in ROTC. There going to expect you to not know how to do a lot of stuff but to still find ways of getting it done. Best thing I can say is ask questions and if you can't find an answer make a decision and press.
I can't really help here beyond saying look up some info on your base and try to get in touch with someone from your det from last year or two if they went there.
You'll be assigned a mentor though you will need to make first contact with your unit. They just get your name, social, and AFSC basically, no info on where your coming from or how to contact you. Just call the base operator and get the phone number from them. You also might as well call lodging and book a room. Just be sure to tell them your on orders so you'll get priority on a room (occasionally can be important).
You can report in any day between your EAD and your RNLTD. Most people will use there RNLTD unless it falls on a weekend, then show the last workday prior. Your sponsor will coordinate this with you so they'll know when to be there. If you are going direct to a UPT base your sponsor will be (or was for the last few classes) from the OSS. They may or may not be rated.
Most bases will have some sort of intramural or squadron sports.
Just remember Exit 6 and Exit 9. If it's not at one of those you probably don't want to go there. Enjoy the drinking and good luck staying awake in the big blue bedroom.
I'm livin the bachelor life so i'll pass on this one.
You don't actually "report in" like ROTC does. You just kinda walk in, say hi, and go around shaking hands. Show up in the UOD (BDU's usually). See my answer to Q4 above for the last part.
Relax. Everyone gets stressed out about it but it's not really a big deal. Just remember that you don't know as much as you may think but you'll still be expected to make decisions and take lead on some projects.
Most of that first day will be spent sitting at MPF waiting to get your CAC. The rest of the time will be filling out paperwork to get your email set up, meeting the people in your office, possibly a short base tour, and if you're really lucky, CBT's.