Bhakthi Yoga is the path for those who develop a permanent association with the Paramathma, through unconditional surrender of the self. 

Srimad Bhagavatham has been compaosed specifically for those who choose this path.  Although it is an independant path, the total surrender to the supreme cannot happen without minimal knowledge and experience of the other two paths.

The following is an extract from Wikipedia:

Bhakti yoga (Devanāgarī: भक्ति योग) is a spiritual path or spiritual practice within Hinduism focused on the cultivation of love and devotion toward God. It has been defined as a practice of devotion toward God, solely motivated by the sincere, loving desire to please God, rather than the hope of divine reward or the fear of divine punishment.^[1] It is a means toward a state of spiritual liberation or enlightenment through the "realisation", or the attainment of "oneness" with God.^[2] Bhakti yoga is often considered by Hindus to be the easiest way for ordinary people to attain such a spiritually liberated state, because although it is a form of yoga, its practice is not as rigorous as most other yogic schools, and it is possible to practice bhakti yoga without needing to become a full-time yogi.^[1]

The Bhagavad Gita, the Bhagavata Purana and the Puranas are important scriptures that expound the philosophy of bhakti yoga.^[2][3] Hindu movements in which bhakti yoga is the main practice are called bhakti movements – the major schools of which are Vaishnavism, Shaivism, and Shaktism.^[4]

 

It has been said in Srimad Bhagavatham that Bhakti Yoga is the Paramathma's primary choice of path leading upto him. 

Narada tells Veda Vyasa in Srimad Bhagavatham:   “Let me repeat what I said before. Karma Yoga which you have taught in theMahabharata, Gnyana Yoga which you have taught in the Upanishads and the Karma Kanda you have described in the Vedas: not one of them will grant Man, so easily, the peace and tranquility which Bhakti Yoga gives.  So dear friend, let your composition be the raft which will save Men floundering in the ocean of pain, frustration and despair.”

Bhakti Yoga signifies the permanent fixation of the mind on the supreme being.  Tapas is one of the primary expressions of devotion.  

Complete surrender also implies the establishment of a permanent communication channel with Easwara.  The mind is devoid of personal desires and needs at this point. The mind is surrendered and is now receptive to all the teachings and guidance provided from above.  The individual is then ready to take the next step towards Moksham. 

Bhakthi is an essential ingredient for all paths. It is not possible to acquire Gnanam or practice Karma, without having a solid foundation of Bhakti.  As C.  Rajagolachari had said (in his introduction to Bhaja Govindham), that: "Knowledge without Bhakti is useless tinsel).