What is repentance & how does one repent?

The best answer on the subject is from the works of Joseph Siess.

The first essential element of Christianity is repentance. The easiest way to show what this is will be to show what it is not.

First, it does not consist of a mere confession of sins. This is a part but not the whole. A man may condemn himself in the most debasing language, sit in sackcloth and ashes, all without avail. The Pharisees confessed sins after the manner of their formalism daily, but very few of them repented.

Second, it is not sorrow and weeping on account of privations and distress brought upon us by our sins, to be regarded as genuine repentance. We may be sorry for a course of conduct because it brought us into serious difficulties, and not hate that course of conduct itself. Esau wept for the consequences but not for their cause.

Third, it is not the occasional meltings of natural affection. Some are constitutionally more soft and yielding than others. A sermon may dissolve them to tears, a tale of the Savior’s sufferings may melt them to tenderness but never bring them to repentance. Orpah wept and lamented and then returned to the Moabites and their idolatry.

Fourth, it is not deep conviction and remorse for sin. Felix trembled under the pungency of his conviction, but turned away from the  light. Judas was overwhelmed with remorse but landed in hell.

Fifth, it is not a glad hearing of the gospel, a compliance with its outward requisitions. Herod heard John gladly, and did many things which he taught, but afterward beheaded him for the gratification  of his woman.

True repentance embraces conviction of sin, contrition for  sin, confession of sin and abandonment of sin. Different individuals may  experience these states of mind and these dispositions of heart in  different degrees according to their various constitutions and  temperaments, the history and intellect, but in every instance they are  indispensable qualities of a genuine penitent.

When convicted of sin, the individual clearly sees and deeply  feels his natural depravity and practical wickedness: his conscience, awake to guilt and exquisitely sensitive, becomes painfully oppressive; and his spirits droop under the dread of final condemnation and endless punishment. This conviction is wrought by the agency of the Holy Spirit through the instrumentality of scriptural truth. That it is not a natural and original operation of the mind itself, is evident from the indisputable fact, that the uniform tendency of sin is to darken the mind, harden the heart, and scar the conscience. The longer the sinner persists in transgression, the more his moral blindness and insensibility will increase. But the state of conviction implies light and tenderness and a quick conscience. Hence, no man need doubt that these circumstances are sufficient indications of the presence and action of the Holy Spirit. The part of man in this is to receive the  truth in love of the truth and to submit to the will of God as directed by the convicting word.

Copied from James Knox's website http://www.jameswknox.org/our-ministry-to-you/faq/