Alcohol has historically played an important social role in Japan, and it's interesting to examine some of the customs that have grown up around it. Alcohol "lubricates" human relationships, and Japanese companies always have formalized functions in which employees will come together as a group to eat and drink -- even if the "drinking" is just oolong tea and not something stronger. One alcohol-related custom I like is the general agreement that whatever one says or does while inebriated shall be forgotten by everyone the next day, something I find very civilized indeed. In most situations, it's considered bad form for a person to pour their own sake or beer. Doing so is called tejaku (teh-jah-koo), and it's the subject of more than a few sad enka songs (iTunes Japan link) about men drinking in a lonely bar after their wife has run away with another man. Instead of pouring for yourself, friends drinking together will always pour beer for each other, which turns drinking into a fun social activity that makes everyone feel better. You can learn a lot about how foreigners are acculturating to Japan by going drinking with them. If they're physically unable to pour beer into their own glass, as I am, that's a person who's probably been in Japan too long. Inversely, there are some foreigners here who will specifically state, "We're gaijin and we're going to drink like gaijin!" as they pour their own beer.
Japan has some interesting social customs related to alcohol.