Dear C.,
Before leaving this world Jesus gave his disciples a final reminder of the good news he had brought them, "that repentance and forgiveness of sins is to be proclaimed in his name among all nations" (Luke 24:47). Repentance and forgiveness were very good news, but the problem is that we easily make them into bad news for ordinary people.
In the Old Testament the Hebrew word for repentance (shubh) merely meant "turning." It is like turning a satellite dish towards God. In a party where everyone is chattering about this and that, if there is one person we really want to talk to we go and say "could I have a word with you." With God it is as simple as turning to him and saying "could I have a word with you, or rather from you."
Satan likes to confuse us by telling us that we must feel really bad about our sins. We must examine ourselves and dig them up one by one, get absolution from a priest or counsellor, and we can never be forgiven unless we are determined never to sin again. Nowhere in the Gospels does Jesus say any such thing.
It is easy to misunderstand the words "Lord have mercy" as if we are criminals who need to cringe before God to be pardoned. The word "mercy" is a translation of the Hebrew word khesed which means "unmerited kindness." I once heard Virginia Mollenkott give this definition of grace: "There is nothing you can do to make God love you more, and there is nothing you could ever do to make God love you less."
Or as Paul said, "By grace you have been saved through faith, and this is not your own doing; it is the gift of God - not the result of works" (Ephesians 2:8,9). So, in answer to your question, there is nothing whatever you have to do to repent properly. You can turn to God anywhere, however bad you are, whatever mess you are in, and without making any promises that you know you cannot keep. As you turn to him God says "I love you totally just as you are, and the Holy Spirit will in due course work in you the perfecting of my kind of love. All you can do is to welcome it."
Bob.