Liberation means to become free from dehatma- buddhi

From Srila Prabhupada's purport to SB 2.4.2:

To become liberated means to become free from dehātma-buddhi, the illusory attachment for personal bodily coverings and everything connected with the body, namely wife, children and all other entanglements...........Devotion for Lord Kṛṣṇa means negation of all material attachments as detailed above. By the grace of Lord Kṛṣṇa, Mahārāja Parīkṣit was awarded all material amenities and an undisputed kingdom in which to enjoy the undisturbed position of king, but by the grace of the Lord he was able to give up all connections with material attachment. That is the position of a pure devotee. Mahārāja Parīkṣit, due to his natural affection for Lord Kṛṣṇa as a devotee of the Lord, was always executing his royal duties on behalf of the Lord, and as a responsible king of the world he was always careful to see that the influence of Kali would not enter his kingdom. A devotee of the Lord never thinks of his household paraphernalia as his own, but surrenders everything for the service of the Lord. Thereby living entities under a devotee’s care get the opportunity for God realization by the management of a devotee-master.

Lord Krsna's Lotus feet - the source of liberation

Rohini Devi speaks to Draupadi on behalf of all the queens rescued from Bhaumasura 

SB 10.83.40: Rohiṇī-devi, speaking for the other queens, said: After killing Bhaumāsura and his followers, the Lord found us in the demon's prison and could understand that we were the daughters of the kings whom Bhauma had defeated during his conquest of the earth. The Lord set us free, and because we had been constantly meditating upon His lotus feet, the source of liberation from material entanglement, He agreed to marry us, though His every desire is already fulfilled.

SB 10.81.40: Thus seeing how the unconquerable Supreme Lord is nonetheless conquered by His own servants, the Lord's dear brahmana friend felt the remaining knots of material attachment within his heart being cut by the force of his constant meditation on the Lord. In a short time he attained Lord Krsna's supreme abode, the destination of great saints.

From the purport:

Śrī Jīva Gosvāmī mentions that Sudāmā's last trace of illusion lay in the subtle pride of being a renounced brāhmaṇa. This trace was also destroyed by his contemplating the Supreme Lord's submission to His devotees.

Liberation means getting out of the clutches of the subtle body..4.29.61 purport

In 4.29 King Pracinabarhisat inquires from Narada Muni about the transmigration of the soul.
Narada Muni replies to this question:

1. Karma is carried in the subtle body, and as the soul transfers to a new body along with the subtle body and the soul's karma , the living entity feels a sense of continuity
2. Although the gross bodies apparently change, the real root of the gross body — the subtle body of mind, intelligence and ego — is always there
3. When the gross body is finished, the plans of the living entity are taken by the mind, and by the grace of the Lord, the living entity gets a chance to give these plans shape in the next life.
4. By the grace of the Supersoul, the living entity gets remembrance and begins to execute plans begun in the previous life

Srila Prabhupada states in SB 4.29.61 " Liberation means getting out of the clutches of the subtle body...If we train the subtle body in this life by always thinking of Krsna, we will transfer to Krsna Loka after leaving the gross body."

My Notes:

One must train the subtle body to be constantly engaged in thoughts about Krishna.This is possible by constant devotional service and chanting the Holy Names of the Lord with full attention.Service on the bodily platform increases identification with matter. True service is anyabhilasita sunyam.... Thus one must be constantly watchful of their consciousness throughout the day in order that the subtle body does not carry material impressions and does not force the gross body to act on the material platform.Cultivation of an attitude of accountability towards Guru in every action will be very helpful in this regard.

References:

1. It is far easier to engage the gross body in service than to control the mind,and therefore the early stages of learning to practice devotional service are centered on engaging the body. Yet aspiring devotees should note that they must ultimately shift their service from merely physical engagement to deep , mental,intellectual and emotional involvement.True devotion means to replace self centeredness with Krsna centeredness. When desire to please Krishna becomes natural, continuous and full of love, one is no longer a part of this world. - Excerpt "Unveiling His Lotus Feet" Pg 946
2. When one is fully absorbed in Krishna Consciousness, in one stroke he is freed of past and future mental desires.By the grace of Lord Krishna motther Yashoda saw all the universes and planets within the mouth of Krishna .Similarly by the grace of Krsna, a Krsna Conscious person can see all his dormant desires at one one time and finish all his future transmigrations. This facility is especially given to the devotee to make his path clear for returning home, BTG.SB 4.29.69
3. One of the goals of Krsna Consciousness is to break the connection between the soul and both the gross and subtle bodies. Pure devotional service effects the break.-Excerpt "Unveiling His Lotus Feet" Pg 949
4. After understanding Krsna as He is, one can become eligible to enter Kṛṣṇaloka and associate with Him. The mind is the cause of such an exalted position. The mind can also get one a body like those of dogs and hogs. To absorb the mind always in Kṛṣṇa consciousness is therefore the greatest perfection of human life.SB 4.29.76-77