Dash-dancing is performed by tapping the analog stick left and right rapidly while on the ground, effectively dashing to the left and to the right alternately. Characters can turn around while avoiding the dash's turnaround animation at the beginning of their dash. The maximum time a character can dash in one direction and still change direction by dash dancing is the same as the number of frames in his/her initial dash animation - after this animation is over, the character will enter a turnaround animation in which no attacks can be performed.
 Competitive Uses
Characters with long and fast dashing animations, namely Fox, Marth, and Captain Falcon make the most use of the technique. In Melee, dash dancing is used primarily to play mind games with the opponent. By continuously switching directions, the player can make prediction quite a chore for the opponent. Dash dancing can be used in conjunction with throws with low knockback to tech chase. Dash dancing is a also good fake out technique. Players can dash towards opponent and during mid-dash, start to dash dance. This can be used to lure attacks out from the opponent, which can easily be punished during their end lag. Dash dancing can also be jumped out of, allowing players immediate use of SHFFLs and wavedashing.
In Brawl, dash dancing is drastically harder because the initial dash animation is much shorter. In addition, many throws have increased in knockback and decreased in hitstun, making tech chasing much more difficult. As a result, dash dancing is much less useful than it was in Melee as therefore sees little use in competitive play except perhaps in Sonic's metagame, which relies heavily on mindgames and punishment to garner KOs.