Which method of meditation is correct?

The following is an excerpt from a samvaad (dialogue) session with Acharya Prashant.

Questioner (Q): Acharya Ji, I have a question on these four commonly quoted methods- Sāma, Dāma, Daṇḍ, and Bheda. I applied Sāma but it’s not working. The other three I know nothing about, and are not working. No method seems to work. What to do?