Don't expect apologies for being bumped into, and don't offer them
In a place as crowded as Tokyo, jostling is so frequent that "excuse me" is unnecessary, and the person will be gone before you get the words out. They're not being rude, they're just used to it.

Don't thank your server for refills
Constantly thanking the waiter comes across as strange and disingenuous in a culture where attentive service (which you're paying for, after all) is par for the course.

Dress up for a bit
Fashion is fairly Western in Japan, but "you don't see many—how should I say it—mature men in T-shirts and shorts," Fautt says. A polo shirt is about as casual as it gets. Women should go easy on the tank tops.

Don't split checks
Whoever offers the invitation to the restaurant is usually the one who pays and assumes the general duties of host.

Don't wear yukatas outside your hotel
Most hotels here, including the Hyatt, offer guests a cotton kimono, or yukata, in the room. Fautt occasionally finds himself at the elevator, stopping guests who have mistaken them for streetwear. They may look elegant, but they're still pajamas.

Never eat or drink while walking
Although vending machines are ubiquitous, locals buy their soda, drink it by the machine, throw the empty away, and continue on their way. No one eats while walking, and public consumption of alcohol is even worse. "Walking around with a beer makes you look like an idiot," Fautt says.

The Lesson: How to Gift
Gift-giving is an important, highly structured part of Japanese culture. Not only are there two specific gift-giving periods (one in December and one in July), but gifts are given at precise price points depending on the relationship: The recipient must reciprocate with a present equal to half the value of the one he received. Foreigners needn't take part in this ritual, but they'll score points for knowing the rules pertaining to souvenirs (omiyage) and gifts for business associates and hosts. On both business and social occasions, the item should cost about 3,500 yen ($25 or $30). You'll find gifts at that price clearly marked in airports and department stores, although you can also bring the equivalent with you from the United States. The noted food writer and longtime Japan resident Elizabeth Andoh recommends arriving with many small, identical gifts—for example, bottles of New England maple syrup—if you're planning to meet a business associate of a similar rank. "You don't get brownie points for being original," says Andoh. "Any attempt at a personal gift would be a mistake." These tokens are meant to be doled out among subordinates at teatime, not consumed by the associate and his family. On a home visit, bring something like cake (which can be shared) rather than, say, flowers. Your gift will not be opened in your presence unless you've said that it's okay to do so, in which case it will be carefully unwrapped (presentation is paramount here). Although certain presents are reciprocated, souvenirs are not. Those you receive in Japan—and you will receive many—need not be reciprocated. When it comes to gifts, Andoh explains, "the Japanese don't consider personal convenience. The awkwardness of carrying something around is not part of the thinking."