I keep a small notebook with our plans on it, reservation numbers, must dos, FP times, souvenir lists, and all that good stuff. I don't do anything super detailed. Just something generic so I have a plan. If you want to use your phone, if you can, make a dedicated folder in your gallery. Screenshot any important information like a schedule, reservations, etc. and put it in that folder. That way you don't have to scroll through one large gallery of pictures and you won't have to worry about connecting to the internet. It's all in one folder.