>>193
0. The easiest way is to make it your nickname. Most people are willing to comply with nicknames even if they don't know what they mean. Failing that,
1a. Find a cute girl that's Japanese and a little younger than you.
1b. Find somebody who's a Japanophile, it will make your job easier.
1c. Find a cute girl.
2. Become friends. How exactly you become friends is beyond the scope of my advice.
3a. Just ask her to call you onii-chan. It's fairly common in Japan, so she won't think it's weird. Done.
3b. Become closer friends before asking. It might be a bit awkward but she will understand.
3c. You will probably have to make her your girlfriend before she'll comply with such a request, unless you can pass it off as your nickname (see step 0.)
4. If all these fail, change your name to Oniichan.
5. If she still won't call you onii-chan, tie her to a chair and whip her until she does.

>>195
Why do you visit /dqn/?