To this day, I still count myself as having few friends in Japan.  While some of the problem is creating opportunities to meet people post-college (issues that persist outside of Japan as well), part of the problem is clearly cultural as well.  Other than the common charge of cultural chauvinism, there is the obvious feeling that I have very little in common with these people (even when it is clearly not true).  To counter this issue, I have developed my own strategy of finding common interests; baseball, boardgames and books.
Baseball
In 94, I remember being mesmerized by the  Montreal Expos and their fairy tale season.  Finally ready to make their way into the World Series, the players instead went on strike and the team’s owners (who at one point started charging for vitamins) got rid of their championship roster.  I never forgave MLB; heck, even my prized baseball card collection was never again to be opened again, finally being lost last year in a fire.  (Frankly, I cared more about dog-eared and torn comic books being lost).  However, my knowledge of baseball never faded away.  And it provided a valuable way to get into Japanese baseball.
It’s hard to understand the most successful team in Japanese baseball – the Yomiuri Giants.  The Tokyo Dome is often turned into a dull affair with boring Yomiuri Giants fans with their trademark gentle clapping.  A friend of mine derisively described them as 「田舎è‡ã„ã€(rednecks); not an entirely inaccurate reading of the situation.  Giants fandom is generally the result of their games being the only games broadcast throughout vast stretches of Japan’s countryside.  These fans have successfully transformed the game of baseball into golf.
No, give me the Tigers. Perpetual losers of the Central League, they still manage to entertain and have had some of the very best players in the league . Their fans are without a doubt the most passionate, entertaining & energising group in Japan. Keeping aside the shameful issue of violence by a handful at events, they are also the same group of fans that actually celebrate on the streets when they win, and are so famous for their loyalty that there is a word for them – Torakichi (“Tiger Crazy”). Latching onto something like that might seem to be an unwise proposition, but I propose the contrary; adopting an easily displayable common characteristic of the local population also makes it easier for them to reach out and try to communicate.
The results so far are promising. I’ve had a lot of “You like the Tigers?! So do I!” comments after I bought their uniform; I’ve actually made friends with people who live in the same neighbourhood as me (which seems to be a holy grail that my fellow gaijin seem to have problems with). The only problem seems to be… that the gf’s parents are Giants fans.

Sigh.