What are the factors to be kept in view in dhyana?
Ramana Maharshi:
"It is important for one who is established in his Self (atma nista) to see that he does not swerve in the least from this absorption. By swerving from his true nature he may see before him bright effulgences, etc., or hear (unusual) sounds or regard as real the visions of gods appearing within or outside himself. He should not be deceived by these and forget himself."
- Ramana Maharshi
Tradition: Advaita Vedanta
Reference: Spiritual Instruction