The Five Precepts of the Church
The Sunday Duty
The first precept of the Church is "You shall attend Mass on Sundays and holy days of obligation and rest from servile labor." Often called the Sunday Duty or the Sunday Obligation, this is the way in which Christians fulfill the Third Commandment: "Remember, keep holy the Sabbath day." We participate in the Mass, and we refrain from any work that distracts us from a proper celebration of Christ's Resurrection.
The second precept of the Church is "You shall confess your sins at least once a year." Strictly speaking, we only need to take part in the Sacrament of Confession if we have committed a mortal sin, but the Church urges us to make frequent use of the sacrament and, at a minimum, to receive it once each year in preparation for fulfilling our Easter Duty.
The Easter Duty
The third precept of the Church is "You shall receive the sacrament of the Eucharist at least during the Easter season." Today, most Catholics receive the Eucharist at every Mass they attend, but it wasn't always so. Since the Sacrament of Holy Communion binds us to Christ and to our fellow Christians, the Church requires us to receive it at least once each year, sometime between Palm Sunday and Trinity Sunday (the Sunday after Pentecost Sunday).
Fasting and Abstinence
The fourth precept of the Church is "You shall observe the days of fasting and abstinence established by the Church." Fasting and abstinence, along with prayer and alms-giving, are powerful tools in developing our spiritual life. Today, the Church requires Catholics to fast only on Ash Wednesday and Good Friday, and to abstain from meat on the Fridays during Lent. On all other Fridays of the year, we may perform some other penance in place of abstinence.
Supporting the Church
The fifth precept of the Church is "You shall help to provide for the needs of the Church." The Catechism notes that this "means that the faithful are obliged to assist with the material needs of the Church, each according to his own ability." In other words, we don't necessarily have to tithe (give ten percent of our income), if we can't afford it; but we should also be willing to give more if we can. Our support of the Church can also be through donations of our time, and the point of both is not simply to maintain the Church but to spread the Gospel and bring others into the Church, the Body of Christ.
Traditionally, the precepts of the Church numbered seven instead of five. The other two precepts were:
To obey the laws of the Church concerning Matrimony.
To participate in the Church's mission of Evangelisation of Souls.
Both are still required of Catholics, but they are no longer included in the Catechism's official listing of the precepts of the Church.