An ideal devotee serves and pleases Krishna to the highest degree, gratifying His transcendental senses and desires. As Krishna is the supreme enjoyer, satisfying His desires is the way He relishes rasa or relationships. When He relishes that rasa with those who give pleasure to Him without any expectation of getting pleasure in return, then such devotees experience bliss, which is one of the byproducts of devotion.
Lectures from a Disciple, "Serving a Person", Pg 51, 2nd Paragraph
Serving a person is the essence of devotion. Therefore, the impersonalists cannot have devotion. It is very difficult to be devoted to an inanimate object or to an impersonal void. Where is the quality or characteristic of devotion for an entity that has no life, no desires and no personality? When referring to service, Srila Prabhupäda refers to it as devotional service to enhance its real meaning. There is no question of service to God without devotion. Bhakti is therefore translated as devotional service.
Lectures from a Disciple, ""Serving a Person"", Pg 51, 1st Paragraph
Without duplicity means that when dealing with others you should have no personal motive other than wanting to please Krishna and to please the devotee that you trust is serving Krishna. That is real freedom from duplicity.
Collected Letters to Friends and disciples Vol 5, Pg 121, 2nd paragraph.
We should not be so idealistic and think that all devotees should be perfect. Unintentionally they can still make some minor mistake. Or as Prabhupada says in the purport to Bhagavad Gita, tenth chapter, verses 4-5 : "Ksama, tolerance and forgiveness should be practised; one should be tolerant and excuse minor offenses of others."
Collected Letters to Friends and disciples Vol 5, Pg 120, 3rd paragraph.
If a person prefers to be Krishna concious and to not talk prajalpa, should he/she care if others perceive that behavior as being unsocialable? My answer to that would be "no". Let others make such judgements. That is their own problem. But if they are serious sadhakas and they are sincere -- the type of people that you should want to associate with -- the day will come when they will begin to appreciate your prior unwillingness to take part in their prajalpa. If they are not sadhakas and you need to associate with them for reasons other than the direct service of Krishna, then you should simply avoid opening your heart to them. Maintain some small talk with them, but don't forget that your association with them is not for spiritual purposes, but for some other business which needs to be done while you are still in a material body. Affection should be reserved for those who are devotees of Krishna. Affection towards non-devotees is shown by helping them to turn their attention toward Krishna.
Collected Letters to Friends and disciples Vol 5, Pg 119, last paragraph."
By talking about others (which is a perverted reflection of the soul's natural propensity for talking about Krishna), we create enmity because nobody likes to hear that others are talking about them, either indifferently or especially negatively. The soul's nature is to be always speaking about Krishna. When speaking about others , we should always speak in a positive way that is related to Krishna's serrvice. Every soul's propensity is to be engaged in Krishna's service and encouraged by others for the service they render to Krishna. To speak about others for any other purpose is simply an uncontrolled urge to speak unnecessarily. Better we do not speak.
Collected Letters to Friends and disciples Vol 5, Pg 118, last paragraph.
Just like if a person is very sick and has high fever, he doesn't think about eating rich, opulent food, rather he thinks "Which medicine and precautions can cure me?" And then he follows whatever is necessary to make that medicine effective so that he can regain his strength. Similarly if a devotee remains humble, even though he may lose his taste or give up chanting Hare Krishna due to some weakness of heart, but if he is very careful and doesn't blaspheme any living entity for his misfortune, then in due course of time, he will achieve his position again.
We must all, at times in our lives, go through challenging times. Without loving and caring devotee association, it is very difficult to fight off maya alone.
Collected Letters to Friends and disciples Vol 5, Pg 73, 3rd paragraph.
Just the other day I was reading Brhad Bhagavatamrta. In volume 1, chapter 7, Krishna told Satyabhama, "I can never fully repay these devotees [the Vrajavasis], and so I am utterly indebted to them." In the commentary, Sanatana Goswami says that since Krishna cannot repay His debt of gratitude, He constantly looks for small favors He can do for them as a token of His affection. Krishna shows by His example the ways to reciprocate love. Though we cannot imitate Krishna, still, if He looks for small favors as tokens of His affection to those who serve Him, then certainly we should try to do the same.
Collected Letters to Friends and disciples Vol 5, Pg 58, 2nd paragraph.
In the past, devotees were fanatic and this has caused more harm than help, in many cases. People falsely renounced, only to realize that their renunciation was based upon a false sense of relief from suffering rather than being based upon a mature understanding of developing our eternal connection with Krishna.
Collected Letters to Friends and disciples Vol 5, Pg 54, 1st paragraph.