Abstain from meat on Ash Wednesday and and all Fridays, including Good Friday
Fast on Ash Wednesday and Good Friday
Fasting is reserved to Catholics aged 18-59, and traditionally consists of the following, as clarified by the United States Conference of Bishops.
For members of the Latin Catholic Church, the norms on fasting are obligatory from age 18 until age 59. When fasting, a person is permitted to eat one full meal, as well as two smaller meals that together are not equal to a full meal. The norms concerning abstinence from meat are binding upon members of the Latin Catholic Church from age 14 onwards.
Besides those two basic rules, Catholics are allowed to choose their own penitential disciplines during Lent.
The divine law binds all the Christian faithful to do penance each in his or her own way. In order for all to be united among themselves by some common observance of penance, however, penitential days are prescribed on which the Christian faithful devote themselves in a special way to prayer, perform works of piety and charity, and deny themselves by fulfilling their own obligations more faithfully and especially by observing fast and abstinence,
In addition to abstaining from meat on Ash Wednesday and Fridays, and fasting on Ash Wednesday and Good Friday, Catholics are obligated to do some sort of penance during Lent. This is something that must be done on their own, and a local priest or spiritual director will often advise a person on their Lenten disciplines.