A couple of tips:
We all had 'suica' cards when I went, which are like oyster cards but they can also be used to purchase food and other items from 7/11 stores (and maybe some other stores I can't remember). This made paying for things a lot easier, particularly as it could be difficult to count out coins in a rush.
Try to learn some Japanese. When we were waiting for trains, we often wanted to check we were on the right platform but most people I approached didn't speak English and would try to avoid conversation. Once I got into the hang of practicing Japanese they were all very willing to help.
Hope you have an amazing time! 😁
Agree about Suica, else you will end up with a pocket full of coins if you are using Tokyo subway a lot, which I heartily recommend. Beware that some stations are vast, allow time, especially at rush hour and you will get lost. Even stations on a single line can have many exits, which can be great if you know the right one for your destination. If you are visiting anyone that's not a tourist destination, get them to fax/email a map or at least Japanese directions. Hotel can help with this too. Because Japanese street numbers are not consecutive. Something like 3-17-46 is the prefecture, district and plot number -I think I remmber that right, so 20 and 22 are never next door!
As for people not wanting to help, Japanese are generally enormously helpful. But their psyche is to avoid embarrassment. So not speaking English, or not knowing the answer to your question and having to say "no" is a big deal. Remembering this will help you phrase questions and inform your encounters!
Can I say one last thing about some of the comments on here about Fukushima, Hiroshima and Nagasaki. I'm a mature student, but both the recent Fukushima disaster, and WW2 bombings of H and N, were massive world events. And Hiroshima was on the news just two weeks ago with Obama's visit. If you're reading this and don't at least know the basics of this history, inform yourself. Travel wisely, you will learn more.