How do ordinary lay people receive Communion? In the hand or on the tongue, with a caution:
[92.] Although each of the faithful always has the right to receive Holy Communion on the tongue, at his choice,[Cf. GIRM 161] if any communicant should wish to receive the Sacrament in the hand, in areas where the Bishops’ Conference with the recognitio of the Apostolic See has given permission, the sacred host is to be administered to him or her. However, special care should be taken to ensure that the host is consumed by the communicant in the presence of the minister, so that no one goes away carrying the Eucharistic species in his hand. If there is a risk of profanation, then Holy Communion should not be given in the hand to the faithful.[Congregation for Divine Worship and the Discipline of the Sacraments, Dubium: Notitiae 35 (1999) pp. 160-161]
The judgment of risk is always difficult. Taking Communion in the mouth is no guarantee if a person had a strong intent for sacrilege or other similar purpose. But it tends to rule out a casual or accidental point of inappropriateness.
I was unaware of the suggestion of the plate:
[93.] The Communion-plate for the Communion of the faithful should be retained, so as to avoid the danger of the sacred host or some fragment of it falling.[Cf. GIRM 118]
Communion ministers in my parishes have always been oriented as to what to do should something fall, spill, or be dropped. There’s not much of a difference if something lands on the floor or on a plate. Most plates I’ve seen are small and shiny, and there’s more of a danger, perhaps, of a host sliding off. It would require an additional number of lay ministers, in some places a number beyond the available altar servers. This sort of thing is really best left for a parish to determine.
[94.] It is not licit for the faithful “to take . . . by themselves . . . and, still less, to hand . . . from one to another” the sacred host or the sacred chalice. [Cf. GIRM 160] Moreover, in this regard, the abuse is to be set aside whereby spouses administer Holy Communion to each other at a Nuptial Mass.
Spouses giving one another Communion: I’ve seen it, but not too often. It strikes me as possibly a poor idea, and not quite to the level of “abuse.”
The question comes up often for Saturday worshipers, and the occasional liturgical minister:
[95.] A lay member of Christ’s faithful “who has already received the Most Holy Eucharist may receive it again on the same day only within a Eucharistic Celebration in which he or she is participating, with due regard for the prescriptions of can. 921 § 2.” [Cf. Code of Canon Law 917; Pontifical Commission for the Authentic Interpretation of the Code of Canon Law, Response to Dubium, 11 July 1984: AAS 76 (1984) p. 746]
Twice in a day is acceptable, provided one is “participating” in the second Mass. I would interpret that as being at Mass in the assembly, and not necessarily in a serving role. A Saturday wedding or funeral, plus the Saturday night Mass comes to mind as the most common example. A music minister on duty at two weekend Masses, another.