With Lent quickly approaching on February 17th, it's time to examine our consciences and make a good confession.  While frequent confession is recommended for everybody, the Church requires that we make a confession of our sins at least once each year.

From the blog of Fr Z at What Does The Prayer Really Say

Fr. Z’s 20 Tips For Making A Good Confession   o{]:¬)

We should…

  1) ...examine our consciences regularly and thoroughly;
  2) ...wait our turn in line patiently;
  3) ...come at the time confessions are scheduled, not a few minutes before they are to end;
  4) ...speak distinctly but never so loudly that we might be overheard;
  5) ...state our sins clearly and briefly without rambling;
  6) ...confess all mortal sins in number and kind;
  7) ...listen carefully to the advice the priest gives;
  8) ...confess our own sins and not someone else’s;
  9) ...carefully listen to and remember the penance and be sure to understand it;
10) ...use a regular formula for confession so that it is familiar and comfortable;
11) ...never be afraid to say something "embarrassing"... just say it;
12) ...never worry that the priest thinks we are jerks…. he is usually impressed by our courage;
13) ...never fear that the priest will not keep our confession secret… he is bound by the Seal;
14) ...never confess "tendencies" or "struggles"... just sins;
15) ...never leave the confessional before the priest has finished giving absolution;
16) ...memorize an Act of Contrition;
17) ...answer the priest’s questions briefly if he asks for a clarification;
18) ...ask questions if we can’t understand what he means when he tells us something;
19) ...keep in mind that sometimes priests can have bad days just like we do;
20) ...remember that priests must go to confession too … they know what we are going through.

According to the Catechism of the Catholic Church,

When Christ's faithful strive to confess all the sins that they can remember, they undoubtedly place all of them before the divine mercy for pardon. But those who fail to do so and knowingly withhold some, place nothing before the divine goodness for remission through the mediation of the priest, "for if the sick person is too ashamed to show his wound to the doctor, the medicine cannot heal what it does not know."  -CCC 1456

And

Without being strictly necessary, confession of everyday faults (venial sins) is nevertheless strongly recommended by the Church. Indeed the regular confession of our venial sins helps us form our conscience, fight against evil tendencies, let ourselves be healed by Christ and progress in the life of the Spirit. By receiving more frequently through this sacrament the gift of the Father's mercy, we are spurred to be merciful as he is merciful:

Whoever confesses his sins . . . is already working with God. God indicts your sins; if you also indict them, you are joined with God. Man and sinner are, so to speak, two realities: when you hear "man" - this is what God has made; when you hear "sinner" - this is what man himself has made. Destroy what you have made, so that God may save what he has made. . . . When you begin to abhor what you have made, it is then that your good works are beginning, since you are accusing yourself of your evil works. The beginning of good works is the confession of evil works. You do the truth and come to the light.  -CCC 1458

For further reading:

The Sacrament of Penance from fisheaters.com

Catechism of the Catholic Church - The Sacrament of Penance