What kind of attitude required to enter in Vaikuntha?

It is very nice to learn that both you and Satsvarupa have highly praised Tamala Krishna. Similarly, Tamala Krishna has also highly praised you and Satsvarupa. This attitude should be maintained amongst your Godbrothers. That will elevate us more and more to the top of devotional service. This is called Vaikuntha attitude. In the Vaikuntha factually there is no fault in anyone, but there is another type of competition. The competition is that one devotee thinks of other devotees how nicely they are serving the Lord. In the material world, the attitude is that everyone likes to think that I am doing better than others. This is material conception. In the Spiritual Sky, it is just the opposite: Everyone thinks that my contemporary devotees are doing better than me. We are trained to address Godbrothers as Prabhu, which means Master. This means we shall try to find out always the serving side of our Godbrothers. Sometimes there are misgivings, but that we should try to overlook.

(Letter to Brahmananda — London 15 November, 1969)

Candanacarya: One time, Srila Prabhupada, you said, “I will go to hell,” but none of your disciples accepted that. Prabhupada: No, I am not in hell. I am with the devotees, so how can I say I am in hell? [laughs] Narottama Dasa Thakura says, “My duty is to serve my guru and live with the devotees.” That is Krsna’s grace. “My mission is to serve my guru, but live with the devotees.”
“This is my desire, life afterlife.” A guru or bhakta does not aspire that he is going to Vaikuntha, Krsna. “Never mind.” But their only desire, his only desire, is that to serve the predecessor acarya and live with a devotee. That’s all. This is the only ambition. The place where the devotees are glorifying the Lord, Krsna is there. So if Krsna is there with the devotees, then wherever devotees are there, that is Vaikuntha. That is Vaikuntha.
Just like our temple. It is Vaikuntha. Because the devotees are chanting the glories of the Lord, that is Vaikuntha. Vaikuntha is not limited. As Krsna can expand Himself, similarly, Vaikuntha can also be expanded, Vrndavana can expand. So wherever there is Krsna, that is Vai… And where is not Krsna? And that is to be appreciated. Then if anyone appreciates Krsna everywhere, then he is living in the Vaikuntha; he is not living in hell or Los Angeles.
Svarupa Damodara: …where pure devotee goes, that place is immediately purified as soon as he is there.
Prabhupada: Yes, because Krsna helps. As soon as the pure devotee sings, Krsna immediately comes there. So it becomes Vaikuntha. Wherever Krsna topics are there, it is as good as Vaikuntha or Vrndavana.

(Morning Walk — December 15, 1973, Los Angeles)

The Vaikuntha mentality is that if one is serving—I have read it in Bhagavata—Krsna better than somebody else, he would simply appreciate that “Krsna has so much favored him. Oh, how fortunate he is. When I shall be able?” That is Vaikuntha mentality. And the material mentality is, “Oh, he has advanced so much. How to cut down him?” That is material. This is the difference between Vaikuntha mentality. So his business is how to cut down. So he is not a Goswami. At least I will not accept. This is the definition of Gosvami. [NoI 1]. So he has not proved to be very dhira. So that is my regret, that these people cannot appreciate the service of a Vaisnava. They are simply personally interested. Personally interested in the materialistic way of life. Everybody is personally interested.

(Room Conversation — February 14, 1974, Vrndavana)

When we are free from designation, when we are purified, then we can unite in the service of the Lord, Krsna. That is real unity. Hrsikena hrsikesa-sevanam… [Cc. Madhya 19.170].
[Bhakti, or devotional service, means engaging all our senses in the service of the Lord, the Supreme Personality of Godhead, the master of all the senses. When the spirit soul renders service unto the Supreme, there are two side effects. One is freed from all material designations, and one’s senses are purified simply by being employed in the service of the Lord.] That is Vaikuntha platform. Just like in Vaikuntha the Vaikunthesvara, Narayana, or Krsna, He’s the central point of service.

(The Nectar of Devotion — November 2, 1972, Vrndavana)