-That being said, manners are often modified when dealing with gaijin to fit gaijin manners, and nihonjin rarely expect gaijin to use spot-on Japanese manners. In fact, they may find spot-on Japanese manners a tad unnerving (just speculating here). A Japanese businessman may shake a Westerner's hand where they would normally bow.
-If you are female, expect to be accorded less rights and priveleges than you are used to. If you are female and white, expect a lot of interest from men.
-Food-wise, be careful to look at the prices of groceries. Some things will be cheaper than you're used to. Other things, such as fruit, will be shockingly expensive. You'll have to adjust your diet to prices.
-You'll also have to get used to eating a lot of Japanese food, including some Japanese foods not generally served in Western Japanese restaurants. You can try to continue eating a lot of Western food, but it may be tough. Most Japanese Western restaurants really suck, as the recipes are significantly altered to fit Japanese taste buds. Pasta sauce, for example, is generally thin as soup broth. Many standard Western ingredients may be difficult to get, though some will be cheap and easy to get.
-Keep in mind that Japanese convenience stores, unlike American ones, actually carry healthy foods (as well as unhealthy ones). However, Japanese candy is REALLY good, which sucks for anyone trying to stay healthy.
-If you want to live in a city with a lot of international influence, and where you may not be looked down on quite so much for being gaijin, Kobe is nice. It's small (pop1.5 million), hilly and pleasant (and the home of Japan's best baseball team, the Tigers). It's got some gorgeous modern architecture, though there's not much in the way of historical landmarks. The great thing about Kobe is that it's part of the same metropolitan sprawl with Osaka - a sleek, hypermodern, industrial city with a VERY cool art museum and lots to do - and Kyoto, a very traditional, quiet and pleasant city absolutely filled with historical buildings and temples, but with very little nightlife or excitement. Kyoto is a bicyclist's paradise, and the bike is the transport of choice there. The three cities balance each other out. Near Kyoto is Nara, the first capital of Japan and home of one of the country's most beautiful and oldest temples.