SB 3.29.18

ādhyātmikānuśravaṇān
 nāma-saṅkīrtanāc ca me
ārjavenārya-saṅgena
 nirahaṅkriyayā tathā
Synonyms: 
ādhyātmika — spiritual matters; anuśravaṇāt — from hearing; nāma-saṅkīrtanāt — from chanting the holy name; ca — and; me — My; ārjavena — with straightforward behavior; ārya-saṅgena — with association of saintly persons; nirahaṅkriyayā — without false ego; tathā — thus.
Translation: 
A devotee should always try to hear about spiritual matters and should always utilize his time in chanting the holy name of the Lord. His behavior should always be straightforward and simple, and although he is not envious but friendly to everyone, he should avoid the company of persons who are not spiritually advanced.
Purport: 

In order to advance in spiritual understanding, one has to hear from authentic sources about spiritual knowledge. One can understand the reality of spiritual life by following strict regulative principles and by controlling the senses. To have control it is necessary that one be nonviolent and truthful, refrain from stealing, abstain from sex life and possess only that which is absolutely necessary for keeping the body and soul together. One should not eat more than necessary, he should not collect more paraphernalia than necessary, he should not talk unnecessarily with common men, and he should not follow the rules and regulations without purpose. He should follow the rules and regulations so that he may actually make advancement.

There are eighteen qualifications mentioned in Bhagavad-gītā, among which is simplicity. One should be without pride, one should not demand unnecessary respect from others, and one should be nonviolent (amānitvam adambhitvam ahiṁsā). One should be very tolerant and simple, one should accept the spiritual master, and one should control the senses. These are mentioned here and in Bhagavad-gītā as well. One should hear from authentic sources how to advance in spiritual life; such instructions should be taken from the ācārya and should be assimilated.

It is especially mentioned here, nāma-saṅkīrtanāc ca: one should chant the holy names of the Lord — Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare Rāma, Hare Rāma, Rāma Rāma, Hare Hare — either individually or with others. Lord Caitanya has given special stress to chanting of these holy names of the Lord as the basic principle of spiritual advancement. Another word used here is ārjavena, meaning “without diplomacy.” A devotee should not make plans out of self-interest. Of course, preachers sometimes have to make some plan to execute the mission of the Lord under proper guidance, but regarding personal self-interest, a devotee should always be without diplomacy, and he should avoid the company of persons who are not advancing in spiritual life. Another word is ārya. Āryans are persons who are advancing in knowledge of Kṛṣṇa consciousness as well as in material prosperity. The difference between the Āryan and non-Āryan, the sura and asura, is in their standards of spiritual advancement. Association with persons who are not spiritually advanced is forbidden. Lord Caitanya advised, asat-saṅga-tyāga: one should avoid persons who are attached to the temporary. Asat is one who is too materially attached — who is not a devotee of the Lord or who is too attached to women or enjoyable material things. Such a person, according to Vaiṣṇava philosophy, is a persona non grata.

A devotee should not be proud of his acquisitions. The symptoms of a devotee are meekness and humility. Although spiritually very advanced, he will always remain meek and humble, as Kavirāja Gosvāmī and all the other Vaiṣṇavas have taught us by personal example. Caitanya Mahāprabhu taught that one should be humbler than the grass on the street and more tolerant than the tree. One should not be proud or falsely puffed up. In this way one will surely advance in spiritual life.