The norm (traditional method) for receiving Holy Communion is on the tongue; however, the Holy See granted an indult allowing the faithful to receive in the hand (except in cases of intinction).
The new GIRM specifically provides that “the consecrated host may be received either on the tongue or in the hand, at the discretion of each communicant" (160).
This response appeared in Notitiae (April 1999), the official publication of the CDWs, regarding the reception of Communion:
“Certainly it is clear from the very documents of the Holy See that in dioceses where the Eucharistic bread is put in the hands of the faithful, the right to receive the Eucharistic bread on the tongue still remains intact to the faithful. Therefore, those who restrict communicants to receive Holy Communion only on in the hands are acting against the norms, as are those who refuse to Christ's faithful [the right] to receive Communion in the hand in dioceses that enjoy this indult.
With attention to the norms concerning the distribution of Holy Communion, ordinary and extraordinary ministers should take care in a particular way that the host is consumed at once by Christ's faithful, so that no one goes away with the Eucharistic species in his hand.
However, let all all remember that the time-honored tradition is to receive the host on the tongue. The celebrant priest, if there is a present danger of sacrilege, should not give the faithful communion in the hand, and he should make them aware of the reason for way of proceeding.”
"The new manner of giving communion must not be imposed in a way that would exclude the traditional practice."
I also recommend Jude Huntz' article "Rethinking Communion in the Hand":