Be artist.
Draw a human figure.
Make it have feminine features, and no masculine ones.
Show it to guy.
"I like it, she's cute!"
I smirk in the most evil way possible.
"Actually that's a male!"
Guy gets pale as a sheet of paper.
"N-no h-h-homo....?"
But it's too late.
He's gay forever.
All according to keikaku. Translator's note: keikaku means plan.