Every Friday of the year is penitential, not only in Lent.
Abstain from meat on Fridays, or in countries where the bishops permit a substitution, choose another act of penance and actually do it.
All Fridays of Lent require abstinence from meat for Catholics fourteen and older, with no substitution.
Pick something specific. A vague intention to be more penitential is not a penance.
A week with a day of penance in it is shaped by the Cross. Small self denial, kept regularly, is what makes larger self denial possible when something real is asked of you.
Friday has been kept as the day of the Lord's death since the first century, and the Didache already names Wednesday and Friday as fast days.
In 1966 Paul VI allowed bishops' conferences to permit other forms of penance in place of abstinence outside Lent. Many Catholics heard only the first half of that and dropped the practice entirely, which was never what was granted.
Keeping Friday as penitential is an obligation. The form is fixed in Lent and may be substituted elsewhere where your bishops allow it. Serious illness, pregnancy, and hard labor excuse from fasting rules.