Regulations concerning Communion.

Fasting, preparation, reception, and thanksgiving.
The photo shows Carthusian monk-priests making their thanksgiving after Communion. Theirs is an ancient tradition that emulates St. John leaning back upon Jesus’ chest at the last supper, although this position is anything but comfortable, as I found out when I was with the Carthusians. Nevertheless, it illustrates the beauty of taking time to make a prayerful thanksgiving after Communion. St. Teresa of Avila recommended fifteen minutes of thanksgiving would be appropriate for her nuns, and encouraged it as a proper exercise by which to learn mental prayer. Of course, for most busy people, such a lengthy thanksgiving is not practicable, although a few minutes of deep recollection might be. (I’m not telling anyone how to pray here, just merely suggesting a wonderful practice.)
Times are changing however.
A commenter or two have suggested that certain dissident attitudes, or practices, or even the state of mortal sin, while being an impediment to the worthy reception of Communion, if observed, would mean there would be fewer people receiving Holy Communion. I responded that would not be a bad thing at all.
Penance.
Growing up, frequent, even daily Communion was encouraged and practiced, but the rules were clear, one must be in the state of grace to receive. Hence the lines for confession on Saturdays were very long, and even in small parishes, at least 2 priests were available to hear them. People understood the necessary dispositions for receiving Communion. On Sundays, less than half the congregation approached the Communion rail. You see, the people attended Mass, but they were not obligated to receive Communion.
Fasting.
Preparation also included a lengthy Eucharistic fast. Pius XII lessened the fast from midnight to whenever one was able to receive that day, to 3 hours before Mass. Since Paul VI, we are required to fast only one hour before the reception of the sacrament. Today Fr. Z has a post asking what people think of restoring the 3 hour fast. (Don’t get upset, he is just “asking”.) I personally think it is a good idea - but it isn’t my call - although privately, I’m free to fast as long as I want. I’m also free to not approach the sacrament if I feel I am not properly disposed. (I think it is chiefly self-love and undue regard for human respect that causes people to feel ashamed if they remain in their pew while everyone else approaches the sacrament.)
Kneeling.
News today is that the Holy Father will distribute Communion on the tongue and to those people who kneel. I personally prefer that. These matters have been under much discussion for years in this country - at one point a California bishop said it was a sin to kneel. Crazy people, huh? Thank God for Pope Benedict.