The only friend is Kṛṣṇa. One should try to raise the consciousness of the conditioned soul to the platform of understanding that Kṛṣṇa is his actual friend. If one makes friendship with Kṛṣṇa, one will never be cheated, and he will get all help needed. Arousing this consciousness of the conditioned soul is the greatest service, not posing oneself as a great friend of another living entity. The power of friendship is limited. Although one claims to be a friend, he cannot be a friend unlimitedly. There are an unlimited number of living entities, and our resources are limited; therefore we cannot be of any real benefit to the people in general. The best service to the people in general is to awaken them to Kṛṣṇa consciousness so that they may know that the supreme enjoyer, the supreme proprietor and the supreme friend is Kṛṣṇa. Then this illusory dream of lording it over material nature will vanish.
(Srimad Bhagavatam----3:27:4----purport).

Śrī Advaita Prabhu, who is an incarnation of Mahā-Viṣṇu, is an ācārya, or teacher. All His activities and all the other activities of Viṣṇu are auspicious. Anyone who can view the all-auspiciousness in the pastimes of Lord Viṣṇu also becomes auspicious simultaneously. Therefore, since Lord Viṣṇu is the fountainhead of auspiciousness, anyone who is attracted by the devotional service of Lord Viṣṇu can render the greatest service to human society. Rejected persons of the material world who refuse to understand pure devotional service as the eternal function of the living entities, and as actual liberation of the living being from conditioned life, become bereft of all devotional service because of their poor fund of knowledge.
(Sri Caitanya Caritamrta----1:6:12----purport).

The greatest service one can render to the Lord is to try to infuse devotional service into the heart of the conditioned soul so that the conditioned soul may be released from conditioned life. Śrīla Bhaktivinoda Ṭhākura has said that a Vaiṣṇava is recognized by his preaching work—that is, by convincing the conditioned soul about his eternal position, which is explained here as nija-dharma. It is the living entity's eternal position to serve the Lord; therefore to help one get release from material bondage is to awaken one to the dormant understanding that he is the eternal servant of Kṛṣṇa. Jīvera "svarūpa" haya—kṛṣṇera "nitya-dāsa" (cc.2:20:108). This will be further explained by the Lord Himself to Sanātana Gosvāmī.
(Sri Caitanya Caritamrta----2:20:6----purport).