If you want me to boil it down to a simple rule, then here it is: Don't be obvious. As much as you might want to show off how much you love Gunslinger Girl or Hellsing on a T-shirt, it's going to attract some unwanted attention, some poor reactions, and will do you no good outside of the world of otakudom. Look at the photo above. That's me on a typical day. You wouldn't expect me to be running Japanator, posting about tentacle rape, or having a giant box of hentai from Icarus Comics under my bed.

Now, I can't just say "don't be obvious" and call it a day. Let me give you a few examples, since I'm sure that you need all the hand-holding you can get.

The Eureka Seven shirt

This here is the only shirt that I will willingly wear from Bandai's Surprise Panel at Otakon. I'm sorry, but sailor fuku T-shirts that are two sizes too large fall into that "bad idea" category. The appeal with this Eureka Seven shirt is that unless you already watch the show, you're not going to know just what the robot head on the shirt is, so people just think it's a cool looking robot design. So, in other words, abstract symbols are a good bet for your shirt -- only otaku will be able to identify the nerdiness.

The Hanshin Tigers shirt

This is one of those "geeks in disguise" outfits. Unless you're really  big into Japanese sports, or have been to Osaka before, you're not going to know who the Hanshin Tigers are. So, I can go around and support my favorite Japanese baseball team, and no one will be the wiser to just how much I <3 Japan. Plus, if I ever run into a Japanese person, there's a 50/50 chance they'll come right up to me and want to talk. The other 50%? They know how dedicated Hanshin Tigers fans are, and find them scary.

The Moyashimon shirt

The Moyashimon shirt is like the Eureka Seven shirt, in that it's not plainly obvious that it's from an anime -- but this one is more recognizable to anime fans, and the ladies seem to love it. I always get people coming up to me and asking what are those cute little things, and where did I get the shirt. It's kind of hard to explain the show without disgusting them. "And this one is E-Coli!" Pro-tip: Cuteness will distract people from the nerdiness of the shirt.

The Kansai Gaidai college shirt

For when I want to show off my college pride, or be blantantly obvious about my ability to speak Japanese, I wear this shirt. Oftentimes, people will ask me, with a smug look on their face, if I can even read what my shirt says. Of course, it gives me a chance to rub it in their face. The rule of thumb here is that if you want to wear a shirt with Japanese text, make sure you can read it.

The Devilman shirt

The Devilman shirt I'm wearing here is just too awesome not to wear in public. A gift from the super-awesome Deb Aoki, this shirt is a mix of GAR and Japanese fashion. While the presence of anime is blatant, it's Devilman. Not only that, if I ever get knocked for the shirt, I simply claim that it's from Japan, and all criticism is dropped. The rule here? If the shirt is artistic, then you can get away with the shirt.

There's more than one way to express your love for tentacles and loli -- like the Japanator forums, or the IRC channel, or in your purchasing habits at your friendly local anime store. But wearing shirts that proclaim you're a gaijin or an otaku, or happen to be plastered with Kenpachi's face? Give those clothes away. I'm serious. In a year or two, you'll realize that you don't like that show anymore, or you'll realize just how ridiculous that shirt looks, and it'll sit in your closet for years. It's better off going to a charity or shelter at that point.