There is a document you can get (I'm sure someone here'll be able to link you...) called Joining Instructions. It has a list of items you should have with you at BMQ.
If you're talking about other items that are a great help, like Swifter pads for cleaning, like a shaving brush for rifle cleaning, and like a toothbrush for cleaning the crease on your boots, then I'm sure others can help as well.
My two cents, though, is to not read anything further about BMQ. It's a great experience, and I personally think you should go in and experience it fully. Having an insider's look at it, and whatnot, kind of takes away from the fun aspect of it.