Hands vs. Feet
Although many people bang with their hands, many poskim are of the opinion that one should bang with his feet on the ground.
Saying a Pasuk when Banging
The Medrash Rabbah says that if one does not say “zecher tzadik l’veracha” when he mentions a tzaddik’s name he has transgressed a positive commandment (asei). In addition, if one does not say “shem reshoim yirkav” (or cursed is this and this rosha) when he mentions the name of a rosha, he has transgressed a positive commandment.
Based on this, some poskim suggest that one should say “shem reshoim yirkav” - “the name of wicked people should rot” when making noise at the recital of Haman. Nonetheless, the overwhelming custom does not follow this view, since doing so would constitute as a hefsek of talking during the Megillah (even though the listener did not make a berachah on the Megillah). The reason why banging during the mentioning of Haman is not a hefsek is because it is done for a purpose.
