Of the 1752 Catholic Canon Laws, how many does the average Catholic need to be aware of in order to practice faithfully?
Generally speaking the average Catholic does not need to read Canon Law unless a specific personal reason comes along. Thus this question is basically opinion based.
Each diocese has at least one canon lawyer if particular situations come along.
The Church is not rigoristic in the sense that she insists that Canon Law is mandatory reading. Personally, it makes little sense for the faithful to need to know Canon Law.
The six basic Precepts of the Church are the basic norms for any active Catholic.
The Precepts of the Church are derived from Catholicism’s moral and doctrinal foundations, and are reflected in many ways, perhaps most notably in her canon law and liturgical discipline. The Catechism of the Catholic Church nos. 2041-2043, lists five precepts of the Church, which are discussed below. Because a sixth precept often appears in other listings, it is also discussed herein. Note that the Precepts of the Church focus on external behavior. The interior attitudes that should animate such activities are better discussed in a different context.
Attend Mass on Sundays and on holy days of obligation, and rest from servile labor.
Commentary: Weekly Sunday Mass (as distinguished from the reception of the Eucharist, which is not required here) is obligatory for all Roman Catholics (1983 CIC 1247; some Eastern Catholics have a slightly different discipline). There is, strictly speaking, no such thing as a “dispensation” from the Sunday obligation. There are instead some factors that might excuse Sunday Mass attendance. One thinks of personal illness or serious infirmity, or the need to take care of someone suffering from same, significant travel situations, or certain jobs affecting public safety or welfare. Saturday evening Mass (regardless of the “type” of Mass—say, a wedding Mass—it is) satisfies the Sunday obligation (1983 CIC 1248). Watching televised Masses or joining in other prayer or Communion services do not satisfy the precept, however praiseworthy one’s participation in such optional activities might be (1983 CIC 1248).
Servile labor, which may be thought of as work primarily oriented to sustaining our earthly existence or occupation, is today probably better understood not so much in terms of the physical exertion required, but rather in terms of the orientation of the work. An accountant, for example, might find digging in the garden or cutting the grass (traditionally reckoned servile activities) to be recreational, whereas doing tax returns on Sunday could be servile work for such a person, and should be avoided. For a cashier, playing the guitar is likely recreational, while for a professional musician, practicing on Sunday is probably a work to be avoided.
Confess your sins at least once a year.
Commentary: Catholics above the age of discretion, generally held to be about seven years of age, are required to confess their grave sins to a priest, even one of a different rite, at least once per year, at any time during the year (1983 CIC 989, 991). Strictly speaking, persons free of grave sin are not required to make an annual confession, but all Catholics are strongly encouraged to bring even their venial sins to confession (1983 CIC 988). Certainly persons conscious of having committed grave sins should not delay in seeking absolution notwithstanding the annual nature of the precept. A well-executed “penance service” is a wholesome activity for Christians, but it is not sacramental confession and does not satisfy this requirement. “General absolution”, even if, as is often the case, it is celebrated illicitly, does satisfy the precept, but persons receiving same are still required to confess their grave sins later in individual confession (1983 CIC 962).
Receive the sacrament of the Eucharist at least during the Easter season.
Commentary: This reception of the Eucharist can take place within or outside of Mass. For Catholics in the United States, the period for satisfying this precept has been extended beyond what, liturgically speaking, is the Easter season, to run from the First Sunday of Lent to Trinity Sunday (after Pentecost). By canon law, though, any just cause allows the precept to be fulfilled at any time of the year (1983 CIC 920).
Observe the days of fasting and abstinence established by the Church.
Commentary: The Church’s laws of fast and abstinence have probably never been lighter. Most Fridays throughout the year and the season of Lent are penitential times (1983 CIC 1250), but since shortly after the Second Vatican Council, the external discipline of abstaining from meat on Fridays has been abrogated in favor of the recommendation to perform some other self-imposed penance (1983 CIC 1253). Only on Fridays in Lent are Catholics, aged 14 and older, bound to abstain from meat. On Ash Wednesday and Good Friday, moreover, Catholics aged 18 to 59 inclusive, are also bound to fast, by which discipline, however, they may still take one full meal during that day, and two smaller meals (1983 CIC 1252).
Help provide for the needs of the Church.
Commentary: While the Church has the innate right to require from the faithful whatever is necessary to support its legitimate temporal activities (1983 CIC 1260), in fact it rarely exercises this authority. Rather, it leaves to individual Catholics the right to determine precisely when and how they will assist with the temporal needs of the Church (1983 CIC 222, 1261, 1262, 1266). The obvious lack of specificity in these canons, however, should not be taken as a sign that they may be, for all practical purposes, ignored. Sunday collections, annual appeals, spontaneous offerings, bequests and wills, and so on are all ways that Catholics have to satisfy this precept of support. Note that offerings given for a specific purpose can be used by Church authorities only for that purpose (1983 CIC 1267).
Observe the Church’s laws on marriage.
Commentary: Most adult Catholics live in the married state. While the canons regulating marriage are many and complex (1983 CIC 1055-1165), the first thing to keep in mind about them is that Catholics are not free to pick and choose which aspects of Church discipline on marriage they will observe and which ones they won’t. Even if a Catholic is not married to another Catholic, canon law still regulates the marriage (1983 CIC 1059). Moreover, the laws on marriage are not limited to those rules leading up to the wedding, but they also impact on the conduct of the marriage and on such things as the care and raising of children (1983 CIC 226, 1134-1136).
Source: Precepts of the Church: Basic Norms for Active Catholics