How to Prepare for Confession

Ask God for the Holy Spirit’s help to examine your conscience well by prayerfully reviewing your conduct in light of the commandments and the example of Christ. Tell the priest the specific kind of sins you have committed and, to the best of your ability, how many times you have committed them since your last good confession. Avoid generalizations and inform the priest of any relevant circumstances in which your sins were committed.

You are obliged to confess only mortal sins. Confession of venial sins, however, is very helpful for avoiding future sin, forming our conscience, and advancing in holiness toward Heaven.  By receiving more frequently the gift of God's mercy, we are encouraged to be more merciful.

If you are in doubt about whether a sin is mortal or venial, mention your doubt to the priest. For a sin to be mortal, three conditions must together be met: “Mortal sin is sin whose object is grave matter and which is also committed with full knowledge and deliberate consent.” (CCC 1857)

This short, two-page handout can assist your reflection on this sacrament as an opportunity to reestablish right relationship with God and others, and to recognize your participation in the "structures of sin" which degrade others' lives and dignity.

http://www.usccb.org/about/justice-peace-and-human-development/upload/Penance-handout.pdf