there's a few things, in mine, i put a 'if found' page in case it gets lost. you should put a couple emergency things in case something happens, like healing, or draw what certain plants that grow in your area look like and if they're good or bad. [if they're poisonous] and, something i do, when there are certain things i don't want other people to read, i write in runes.
a goo idea is to keep your original BoS in a binder, and transfer the pages as needed.
As of what to keep in it is hard to say, if your going somewhere i would bring the original. Maybe your phone number (not house phone number, your mobile because you can get a new mobile simply and it's a big hullablu to get a new house phone)
i think you should just put what you might need for that specific trip.
There are many things you put in a BOS your experiences with your meditations,grounding,centering,energy manipulation,closing after your done with your spellwork describe what happens when you perform these basics and how you feel afterwards.
You also can write your spells,notes, how you feel before,during,and after your spells, and or rituals.
As a side note.. Your book of shadows is not only your personal journey in magic but can be a history of your ancestors and those that have helped you to learn. Even though it is called a book it does not have to be a physical book. You can use photo albums, tape recordings etc. to enhance your "B.o.S" however I do recommend you make it personal. Add any touch to it that helps to make it more yours. My written one has decorations and photographs of my path and life through my years of magic :)