I'll ramble a bit. Sorry if this is a little out of sorts.
You can bring makeup and personal products, but they all need to be in their original plastic containers and have an ingredient list, as alcohol can't be one of the 1st three ingredients (I think.). I was one of the few who was allowed to keep my makeup, but In there you don't really need it, but I liked having it because my complexion was horrible. You can't bring any perfumes as other patients may be sensitive to scents. Bring a razor so that you can use it once you are on a higher safety level. Oh, and no glass containers, either. Pretty much just plastic!
Brink a fluffy twin mattress topper as the beds there suck. Also bring your own pillows and a stuffed animal if you wish. I brought one of my favorite blankets as theirs are hospital issue and aren't all that comfortable. You might get cold at night (I know I did!) I advise bringing warm clothing and dressing in layers as the unit tends to be cold, but you may be able to go out on the porch or outside on break (if they still allow it.)
Make sure NOTHING has any metal on it or else it will be confiscated and you won't get it back until you leave. I was allowed to keep a couple of thin metal bracelets and a watch, but others had all jewelry confiscated. So it varies depending on who checks you in.
If you do artwork, you can bring your art supplies (within reason) and they will be kept for you until you check them out to be used in the common area. Some people brought paint sets and such. I also advise bringing a water bottle if you like to drink water throughout the day. They give you cups, but a bottle is nicer because you won't have to worry about it getting knocked over or anything.
If you have visitors who bring you food, just remember you have to eat it within a day or two or it gets thrown away. This helps keeps the kitchen area clean.
You'll go through modules of group therapy, and unless you're there enough time, you'll likely miss some of the information. If you get pulled out of a group for individual therapy, make sure you get the handouts from the group (if there were any), or at the very least ask the group leader what went on in the group. You may discharge from the program before there has been a complete cycle in a type of group therapy, so be sure to ask that you get all of the handouts for that group. Don't wait until the very last minute as it takes time to get all the paperwork together. The same goes for the newcomers group. This group is very important because it will teach you a LOT of different coping skills, so please make sure you get all the paperwork from that group, too. I learned coping skills in that group that I have never even seen mentioned anywhere else!
I don't know if you've been inpatient before, but all in all, it sucks getting used to the fact that you have little freedom. I think I called home every day and cried. (Don't forget to bring a phone card as I'm pretty sure cell phones aren't allowed.) You have to ask to go to the bathroom, you have to ask to do al kinds of stuff that you normally would just go ahead and do for yourself. It sucks, but you WILL learn a lot of coping skills, so I urge you to take advantage of your time there and get the most out of the program. It is so completely different in that you will be able to fast track your healing, and by that I mean that if you tried to learn all of this stuff in an outpatient setting, it would take you years if not longer. There are techs there for you 24/7, so use them, even if it's 3am. Go to the "helping chairs" because this is one of the few times you'll get one on one help in using your coping skills. I know it can be daunting to go and sit in those chairs, but they are there for your use so please use them!
My family got the impression that my time there was horrible, and while I did hate it, I learned more there than anywhere else and if I had to go back into the hospital (knock on wood), I would definitely go there as nobody else knows how to treat trauma patients.
Oh, a few more items to bring. Books! Even if you aren't a big reader, still bring a book or two as you'll have free time and it's nice to just be able to go off and read on your own and not have to be involved with everyone else on the unit. Earplugs! Unfortunately the design of the hospital is such that one wing of the unit is adjacent to the adolescent TBI unit, and they can be loud! Earplugs help drown out any unwanted noise. I'd bring a few sweatshirts, jeans/yoga pants/leggings, t-shirts, etc. Whatever is comfortable to you. Oh, and comfy slippers. I lived in my ugg slippers while I was on the unit. They have washing machines where you can do laundry, so I wouldn't bring more than a weeks worth of clothing.
Its also nice to bring a journal of your own, either one you already use, or a new one. Just not spiral bound or with any metal on it.
Don't try to sneak anything in because they do search your entire bag (with you present) and then check your clothing as well. I've heard of others sneaking in some pretty wild stuff!
I was able to take in my diskman, CD's and a small portable speaker with no wires. (It plugged directly into the headphone jack). I think you may be allowed to have an ipod that is checked out during the day, but I am not sure. You just can't have any headphones with wires, which is why I brought a speaker that plugged directly into the headphone jack. I don't know if you can buy these anymore as I got mine on clearance a long time ago when ipods were transferring from having no speaker to an internal speaker, and thus these external speakers were no longer needed. But, if you bring something battery powered, be sure to bring extra batteries. And if you bring CD's they WILL check the content. My Dane Cook CDs were deemed inappropriate :( But if you just have an MP3 player, they won't check every song.
Bring some money so that you can order take-out with the group once a week, and can buy a little something at the gift store when you go down on break (once you're on a higher safety level).
My advice is to try and not get involved with anyone else's treatment. A lot of other people do this as it distracts from their own treatment. If you're NOT DID, you will get so incredibly annoyed by the staff constantly asking you to "check in with your other parts" but they mean well. It's just that most of the patients do in fact have DID so they kind of just ask everyone that. Be nice and just say something like "there is only one of me, I am not DID and I do not have parts" Really, I got SO sick of saying this by the end! And it messed up with my future treatment at other facilities where I had to be re-trained as to another non-DID concept of parts. Whew!
I know I've said a lot, and I know that some of this stuff has likely changed since I've been there. Please feel free to ask me more questions!