The basic requirement 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.
In the sacrament of penance the faithful who confess their sins to a legitimate minister, are sorry for them, and intend to reform themselves obtain from God through the absolution imparted by the same minister forgiveness for the sins they have committed after baptism and, at the same, time are reconciled with the Church which they have wounded by sinning (CIC 959). 

A serious, grave or mortal sin is the knowing and willful violation of God's law in a serious matter such as violation of one of the Ten Commandments. Venial sin are slight sins. They do not break our friendship with God, although they injure it. They involve disobedience of the law of God in slight (venial) matters.  

The sacramental seal is inviolable; therefore it is absolutely forbidden for a confessor to betray in any way a penitent in words or in any manner and for any reason (CIC 983 §1). 

 Member of the Christian faithful is obliged to confess in kind and number all grave sins committed after baptism and not yet remitted directly through the keys of the Church nor acknowledged in individual confession, of which the person has knowledge after diligent examination of conscience . It is recommended to the Christian faithful that they also confess venial sins
(CIC 988 )

Confession Times:

Sundays: 7:15-7:45
 

A guide for confession