I have everything photocopied as you said. I have one copy with my family, and I'll be taking the other copy with me on the trip. I also will be bringing proof of my hotel stay, flights, and the such. One thing about Japan is, shops aren't allowed to accept any currency other than the yen, so I'll be forced to exchange all the money I have with me at the airport. I'm thinking the worst part will be trying to figure out the subways, but I have some of those mapped out ahead of time, thanks to those handy online subway route thingies they have.
Keep the tips coming, guys!