Standing right in front of the speakers, whether dancing or not. While it may feel really fucking good for the speaker fucker
, this usually diminishes the sound quality for everyone else listening to the music and is generally frowned upon by those who do not speaker fuck. Side-effects of speaker fucking generally include eventual deafness, desensitization to vibration, and feeling really fucking good while you're doing it.
I was speaker fucking for the last ten tracks and my bones are still quakin' from the bass shakin'