Japan is like a little girl who has lost her way. Japan is like a child fighting a dragon. Japan is like a cat on a hot tin roof.
Writers sometimes use these grandiose statements to describe a very complex place or situation and look exceptionally wise while doing so. Usually I think they are full of b.s.
But Japan does appear to have some basic dichotomies: old vs new, young vs old, Pepsi vs coke. In that sense, everyplace is just about the same. (It's true - travel writing is not my forte). So rather than sweeping statements about Japan, I'll just comment on a few different areas.
When you arrive
Expect clean like you've never seen in a city before. I always thought DC had the cleanest metro on earth - it's a bag lady in comparison. Japan metro bathrooms are actually just regular bathrooms that anyone - not just the desperate - would use. Their streets are litter free. Their soda machines often have recycling containers built into them, which is ingenious.
Cleanliness is a cultural institution as well. At every meal you are given a scented towel to clean your hands off with. At shrines you wash your hands in a fountain first. And their toilets... Well, their bathrooms probably merit their own blog post entirely...
People really don't bow that much - in traditional sushi restaurants, occasionally. But that's it.
Some signs are in English, some aren't. People at hotels will know English very well - your average restaurant employee won't. Best to get some words under your belt first. You'll often be the only American that you'll see - especially on the metro. At tourist attractions, though, be prepared to see the people from your hotel over and over again.
Don't worry about food or drink - there are vending machines every 30 feet selling cold drinks and cigarettes. Haven't seen any of those "other", less reputable vending machines yet.
There are also giant, monster crows the size of small cats and with beaks like parrots. They travel in huge flocks are fearless and noisy as hell.
Work attire is very American - suits and ties for me, dresses or skirts for women. Because Japan puts such value on collectivism as opposed to individuality, there is usually very little diversity in what people wear. Men's ties are drab and muted. Women often wear white tops and blue skirts. Children almost universally wear uniforms - often in the sailor style that became very popular after WW II. Older women wear these goofy sun hats that are adorable. And speaking of the sun, women use umbrellas (regular ones, not the fancy ones you think of) to cover themselves from the sun all the time. Often, they'll be riding a bike, using an umbrella, and texting at the same time.
But there are little things people do to stand out. There are millions of phone cases with floppy ears or fun designs on them. Key chains have adorable anime characters on them that stick out of pockets or backpacks. And then there is the famous Harajuku district, which caters to dozens of subcultures, like goth, Lolita, punk, even pirate (I think that one is still catching on, though).