Premanand Maharaj Ji
How do I tell right from wrong, and stay firm on it?
Awaken viveka through satsang and Naam
Until viveka (discernment) awakens, the intellect can even stamp approval on wrong conduct. Chant the Name, do good to others and hear satsang to awaken it.
To awaken viveka, chant the Name, do good to others, listen to satsang, and if you have time, study the scriptures.