I'm visiting Japan (Tokyo) for the first time soon!

I know very little about visiting Japan. I'm trying to absorb some quick advice from websites, but is there anything I should prepare in advance? What do you wish you'd known?

@saraislet if you are planning to travel by train, *buy a JR pass*. It can only be bought from outside Japan, and gives you huge discounts on basically all train travel in Japan. 100% worth it.