Updated: Oct 2, 2019
The Zohar has a long list of suggestions: below some essential that could be powerful.
In order to do TESHUVA-REPENTANCE, a person must know what is sin? According to the Zohar below, SIN separates God from His Nukva/Shechina, Female aspect - the person causes the lower ה to separate from יהוה resulting in ה (Female Aspect) by herself and יהו (God) by Himself - which causes a reduction of the flow of abundance; if it is to the point of NO abundance, the result is death.
Teshuva then is the return of the missing ה to the יהו to create the union of יהוה and thereby restore the flow of abundance. The separation of the ה from the יהו is the direct cause of all disasters including the destruction of the two temples, wars, famines, poor heath, no family, no husband, no wife, no children, no work...
Real TESHUVA-REPENTANCE requires you to be tested in the sin that you committed. How are you going to create these circumstances again? For you it is impossible! Only God can recreate them.
Therefore you have to Pray that God engineers again those circumstances, so that you can be tested and perhaps this time you will not fail.
The Zohar says repent on the sins you remember and the ones you forgot will resurface.This gives us to 2 paths to repentance: One difficult and one slightly easier.