Here is simple line from Ramana Maharshi
The second line – ability to focus within to a single entity ( Maharshi uses the word to a single thought)
Well first one has to find something within where you can focus your attention ( requires a Guru ) –
Then hold to it steadfast
Finally one has to Merge in it. ( conquering ego )
These three steps – when done simultaneously is sayam. And when done – is savikalpa Samadhi
The next step ability to keep unwanted thoughts out is much harder. On a gross level it requires faith God will take care of me. But it is much more. It shows transformation of the mind! What does it transform to?
Good question isn’t it?
Bhavin