More: 5 Tokyo bars for train nerds (yes, they exist)
4. One card is good for all trains and buses
The Tokyo train system is actually a network of three train companies.
Originally, each system required its own tickets.
Now rechargeable Suica and Pasmo cards let riders seamlessly touch their way in and out of all lines.
As of March 2013, paying fares got even easier -- a single card became usable for trains and buses throughout the country. You can get one as soon as you arrive in Tokyo from almost any ticket machine.
The ¥500 deposit (a little over $5) for the card is refundable.
The time you save not calculating ticket costs makes it worthwhile even if you keep the card as a souvenir.
5. There are pockets of quiet everywhere
From temples hidden between office buildings (Hanazono Shrine in Shinjuku is a favorite of these) to the tree-lined canal that runs the length of Nakameguro, you're never far from an oasis of calm in the frantic city.
Winding residential streets lined with walled gardens are often just a block away from busy main roads.
If you take a detour down a little unmarked road (most Japanese streets are unnamed) chances are you'll discover a tiny cafe, quirky neighborhood art project or a jumble of ultramodern condos and rickety ancient architecture.
More: Insider Guide: What to do in Tokyo
6. Japanese bathhouses
Public bathhouses, or sento, are a soothing holdover from a time when most homes didn't have bathtubs.
Whether it's a bright, modern place in Omotesando with fizzy water and fancy soap or a creaky neighborhood bath with a coin-operated hairdryer that's been bolted to the floor since the 1960s, all public baths cost ¥450.
The Tokyo Sento Association is redoubling efforts to make them foreigner friendly ahead of the Olympics by posting etiquette and instruction cards in four languages.
7. That word you keep hearing is 'welcome'
After a few days in Tokyo, you might find yourself asking, "What's that thing they always say when I walk in?"
Whether it's sweaty, aproned guys shouting in unison as you walk into an izakaya (lively restaurants that serve alcohol with lots of small dishes) or one perfectly coiffed woman murmuring as you enter the hush of a small boutique, they're saying the same thing: "Irasshaimase."
It's a polite way of saying "welcome."
Although your instinct may be to reply -- "Thank you?" "Hello?" -- locals insist no response is required. A friendly little bow in response doesn't hurt, though.
8. The sushi really is that good
The famous tuna auction at Tsukiji market starts just after 5 a.m., but the day's 120 free tickets are often all snapped up as early as 4.
Whether you get to the auction or not, the market and surrounding shops will be springing to life around that time -- it's the best place to enjoy an early morning plate of the freshest sushi you've ever tasted.