1. People don't eat while walking, standing, riding the trains/buses.
They all eat while sitting down, or occasionally standing at fast-food standing-only restaurants. If you try to eat any other way they stare at you like you're a weirdo.
Restaurants don't make it very easy for you to obey this rule either ~ most non-westernized restaurants (i.e. Starbucks or McDonald's) don't have anywhere for you to eat...they just sell you the food!

2. Most people don't drive.
I asked many of my Japanese schoolmates and they say most people have driver's licenses, but don't own cars or don't find cars convenient in Kyoto. Almost everyone bikes, and on rainy days or when they want to travel longer distances they use the buses and subways.

3. 6 Different ways to say "May I go to the bathroom?"
Starting from the most formal to the most casual:
- Toire ni ikasete itadakitaindesunga
- Toire ni ikasete itadakemasenka
- Toire ni ikasete moraemasenka
- Toire ni ikasete kudasai
- Toire ni ikasete moraeru/kurenai?
- Toire ni ikasete
Of course, you can use these forms for other questions too. It's just that our last lesson was using "bathroom" as an example.
If it wasn't already obvious, Japanese culture is saturated with rules about polite behavior. They say the idea of a mature adult is one who thinks of the other person, and takes it upon themselves to help that person to the best of their ability (within reason). It's very different from the American 'adults = independent and self-sufficient' idea that I was brought up with.

4. Japan doesn't have a lot of room horizontally, so they build vertically.
When shopping, you don't just look at the ground floor or you'll miss about 90% of the sights. You have to look up.
There are shop signs that go to the tops of shopping buildings, each floor with different things to see. Some of the more popular places I've seen are called Daimaru and Takashimaya. They range from grocery stores to Chanel to traditional Japanese earthenware pottery (all in one building).

5. Fresh food. Every day.
I was always used to grocery shopping about once every 1-2 weeks. The meat would go in the freezer and would always need to be defrosted before cooking. Here it's different.
It seems most people go grocery shopping almost every day (or at least once every 2 days). The food is always fresh in the markets - and they always have expiration dates in very noticeable parts of the packaging.
Fresh fruit is probably the most expensive type of food I've seen so far - almost $1 USD for an orange the size of my fist. Being a cheapass, I've been getting my fruits from fruit juice instead.

6. Bakeries!
EVERYONE eats bread! I don't meant boring slices of wheat or white. I'm talking about a much larger variety, and fresh everyday. There's pizza bread, korokke bread (korokke is a kind of friend potato, but not like french fries at all), curry bread, many variations of bread with red bean paste fillings, melon bread (melon pan)...and many others whose names I can't read yet (*** kanji!).
You could eat bread for all three meals of the day if you wanted to. And it would be filling too, not junk food.

7. Ittadakimasu, Gochisousama
No one does this. Not the way they show it in anime or manga anyway :P. They say it quietly or think it silently, but they don't clap their hands as if in prayer and say it out loud.
When eating at a restaurant and leaving, you might say Gochisousama to the host or hostess.

8. Fast food is FAST.
I mentioned earlier that there are places where you're required to stand and eat. This is mostly for soba/ramen/udon shops. The food comes out within 1-2 minutes of ordering (in most places I've seen, they have you order from vending machines).
They have counters a little above waist height, and you're supposed to stand there and eat. There are no chairs.

9. The Japanese like their sweets.
Find a grocery store? Maybe about half of the place is filled with sweets. There are about a gazillion variations of mochi sweets, and then there are many more western-influenced cakes, pastries, and jellies.

10. The police are there to help.
Unlike in the U.S., where police officers are really high school bullies who never made it past graduation, the ones here actually help you. Whenever someone needs directions, or feels even a little bit uneasy about something (whether or not they have solid evidence etc) they can get help from the police without worrying about being bullied just for asking.