Just a few bits of advice from my experience at Dartmouth...
I would say getting fit is a big one, it wont really help you pass or fail, but will improve your time at BRNC. Im running the 1.5 in about nine and a half mins, and still feel half dead after some of the pt sessions. The RN fitness test level is about 11:10 (give or take a few seconds, i cant remember) but if your hitting over ten and a half you will struggle. Also a good level of fitness helps morale-wise hugely on ABLE, and good morale shines through towards a pass!
As for the amount of stuff you can take, to be honest you have a fair bit of space at BRNC. All your civvies will stay in the baggage store until between weeks 2 and 7 depending on your sea parents. That said I think a lot of people (myself included) underpacked. I took chinos a blazer three shirts and a polo, as well as gym shorts and a t-shirt for the gym. Take some warm clothes (trakkies a hoodie etc...) as you will spend time doing sports like sailing, and shorts and a t-shirt is not enough to keep you warm.
The first few weeks are pretty hectic, keep your head up. Rounds are a big game, learn to play along, your sea parents/DO/DivChief dont want to be wasting their evenings inspecting you any more than you want to be wasting yours cleaning. Some people will get over stressed about little things, and that causes tension within the division which is far worse. Take a sense of perspective, you wont get kicked out for having badly bulled shoes!!!
Be decent to the Arabs. A lot of people treat them like dirt to be honest, and some are pretty crap and the job, that said others are excellent, and in my experience their loyalty to their friends is second to none. Treat them with respect, and you will get valuable friends who will work hard to help you out, treat them badly and they can easily cause you problems.
DO NOT GET COCKY WITH THE OFFICERS! Somone who seems to have little direct bearing on your division or training may take very badly to you answering back or rolling your eyes. Next thing you know they are sitting on the CAG board that decides your fate if you fail ABLE and ALE, and it only takes one negative report about your attitude to get you COMPWFTed (compulsory withdrawl from training). Anyone who was at Dartmouth in the April intake will probably know a citain chap who fell fowl to this!!!
Take good waterproofing for ABLE, canoe bags are great, get about five of them big enough for two or three folded jumpers. I didnt have them, and was horibly envious of everyone who had. You need to be able to pack your things as compact as possible for in your burgan, so try to get the bags with an air valve to get any air out.
Listen to your back-phasers (the people held back from last entry - mainly ABLE failures and injury cases.) they know what BRNC is all about.
For ABLE, get to know how to do PLTs. Learn the NATO sequence of orders to the letter, if you are going to deviate justify what you are doing, and only deviate from the sequence when absolutely neccisary! ("Im not going to use a sequence of phases to get this task done as I feel that the concurrent activity is more important"- When you get near to doing ABLE you will know what I mean!) Learn the buzzwords - phases, concurrent activity, limitations, and say them on every task, several times if possible. ABLE has loads of free marks for using the right phrases. (I realised this and passed 3/3 tasks, so it works!) As long as you pass ABLE and arnt a complete cock you will pass term 1.
As for AIB, its pretty easy when you look back at it. Keep a good attitude, keep positive and in control of yourself, even if things go tits-up. Dont panic, whatever happens, if you look like your comfortable and in control, even if your not, you should be fine. Know your branch and career path in depth, it will help on th intervew immensely (For warefare - BRNC term 1 militerisation, ABLE, BSSC - term 2 IFT 10 weeks on capital ships - Ark Royal, Albion, Ocean then fleet board at the end of IFT, this comprises of oral and written tests about the ship/RN then back to BRNC for MARL then pass out, After that Initial warfare officers course at BRNC for 1 term, followed by initial DOs course SFT nav course etc...) There is a high failure rate, but then there is a lot of crap applicants, be confident, and be prepared and its easy.
Hope this is reasonably helpful, its just some of teh bits that I found really stood out for me, and that your AFCO wont necissarily tell you.
Good luck...