The user puts his hands at his sides and says the syllables "Kameha...", then he charges a blue energy sphere in each hand as he draws his hands forward and says the last syllables "meha!" while he releases the energy spheres and backs away while maintaining the energy spheres' shape and movement. The energy spheres can be controlled using arm movement to be fired against the opponent.
Goku uses this attack during his battle against Frieza in his final form on Namek. After getting kicked down into the ocean by Frieza, Goku discovers that Frieza uses his eyes to follow Goku's movements instead of sensing his energy. Testing this possibility, Goku fires up his Twin Dragon Shot one by one at Frieza. Frieza mistakes the Twin Dragon Shot for Goku, but he still manages to dodge the attack. However, this is merely a distraction for Goku to emerge from the ocean unseen and double kick Frieza down into a cliff from behind. However, the plan proves useless, as Frieza does not suffer any damage in the slightest, however he does manage to surprise Frieza as he tells Goku he was the first one to get him dirty other than his parents. 
Gohan tries this underwater attack against Dabura. After getting blasted into the water by Dabura's Evil Impulse, Gohan charges two Kamehameha spheres from each hand and fires them one after another. Gohan guides the spheres out of the water to Dabura, who deflects them and blasts Gohan again with the Evil Impulse.
Appearances in games
Twin Dragon Shot is named in Dragon Ball Z: Supersonic Warriors 2. It is initiated when Goku is below his opponent, and has the ability to home in on the enemy. The second blast can also be charged up. Like most moves in the game, it costs 50% of the player's current ki level. It is called Guided Kamehameha in Super Dragon Ball Z.