Text 25

sanaih sanair uparamed
buddhya dhrti-grhitaya
atma-samstham manah kritva
na kincid api cintayet 

Translation 

Gradually, step by step, one should become situated in trance by means of intelligence sustained by full conviction, and thus the mind should be fixed on the self alone and should think of nothing else. 

Commentary by Srila Prabhupada 

By proper conviction and intelligence one should gradually cease sense activities. This is called pratyahara. The mind, being controlled by conviction, meditation, and cessation from the senses, should be situated in trance, or samadhi. At that time there is no longer any danger of becoming engaged in the material conception of life. In other words, although one is involved with matter as long as the material body exists, one should not think about sense gratification. One should think of no pleasure aside from the pleasure of the Supreme Self. This state is easily attained by directly practicing Krishna consciousness.

Commentary by Sri Visvanatha Cakravarti Thakur
(combined commentary for verses 24 and 25)

In such practice of yoga, the first and last actions are mentioned in two verses (24-25).

The first action is to give up desires and the last action is not to think of anything at all.