Confession is meant to be a sincere moment of conversion, an occasion to demonstrate trust in God's willingness to forgive His children and to help them back on the path of following Jesus.
~Pope Francis
The Catholic Church teaches us that the Sacrament of Penance (sometimes called Reconciliation or Confession) is a grace-filled opportunity to celebrate God’s forgiveness. We are called to a true sorrow for the sins we have committed, along with an intention to repair our lives and our relationships with God and our community.
We prepare ourselves by taking time for prayer and reflection with an Examination of Conscience or "prayerful self-reflection on (one's) words and deeds in the light of the Gospel to determine how (one) may have sinned against God." (USCCB)
The USCCB provides several different Examinations online, for different ages, for single or married people, so you can prepare ahead. A handout will also be available for your use in church on Wednesday.
The confession of evil works is the first beginning of good works. You do the truth and come to the light. - St. Augustine