The basic requirment for a good confession is to have the intention of returning to God like the "prodigal son" and to acknowledge our sins with true sorrow before the priest. 

Sin in ones own Life
Todays world has lost a sense of sin. As followers of Christ, we must make an effort to recognize sin in daily actions, words and omissions. 
The Gospels show how important is the forgiveness of our sins.  

The Differences in Sins
Actual sin is sin which people commit. There are two kinds of actual sin, mortal and venial.
Mortal sin is a deadly offense against God, so horrible that it destroys the life of grace in the soul. Three simultaneous conditions must be fullfilled for a mortal sin: 1) the act must be something very serious; 2) the person must have sufficient understanding of what is being done; 3) the person must have sufficient freedom of the will. 

Examination of Conscience
Before going to confession you should make a review of mortal and venial sins, and should express sorrow for sins, hatred foe sins and a firm resolution not to sin again. 
A helpful pattern for examination of conscience is to review the 10 Commandments and the Precepts of the Church:

1. Have God and the pursuit of sanctity in Christ been the goal of my life? Have I denied my faith? Have I placed my trust in false teachings or substitutes for God? Did I despair of God's mercy?
2. Have I avoided the profane use of God's name in my speech? Have I broken a solemn vow or promise?
3. Have I honored every Sunday by avoiding unnecessary work, celebrating the Mass (also holydays)? Was I inattentive at, or unnecessarily late for Mass, or did I leave early? Have I neglected prayer for a long time?
4. Have I shown Christlike respect to parents, spouse, and family members, legitimate authorities? Have I been attentive to the religious education and formation of my children?
5. Have I cared for the bodily health and safety of myself and all others? Did I abuse drugs or alcohol? Have I supported in any way abortion, "mercy killing," or suicide?
6. Was I impatient, angry, envious, proud, jealous, revengeful, lazy? Have I forgiven others?
7. Have I been just in my responsibilities to employer and employees? Have I discriminated against others because of race or other reasons?
8. Have I been chaste in thought and word? Have I used sex only within marriage and while open to procreating life? Have I given myself sexual gratification? Did I deliberately look at impure TV, pictures, reading?
9. Have I stolen anything from another, from my employer, from government? If so, am I ready to repay it? Did I fulfill my contracts? Did I rashly gamble, depriving my family of necessities?
10. Have I spoken ill of any other person? Have I always told the truth? Have I kept secrets and confidences?
11. Have I permitted sexual thoughts about someone to whom I am not married?
12. Have I desired what belongs to other people? Have I wished ill on another?
13. Have I been faithful to sacramental living (Holy Communion and Penance)?
14. Have I helped make my parish community stronger and holier? Have I contributed to the support of the Church?
15. Have I done penance by abstaining and fasting on obligatory days? Have I fasted before receiving communion?
16. Have I been mindful of the poor? Do I accept God's will for me?