SB 10.47.24

dāna-vrata-tapo-homa
 japa-svādhyāya-saṁyamaiḥ
śreyobhir vividhaiś cānyaiḥ
 kṛṣṇe bhaktir hi sādhyate
Synonyms: 
dāna — by charity; vrata — strict vows; tapaḥ — austerities; homa — fire sacrifices; japa — private chanting of mantras; svādhyāya — study of Vedic texts; saṁyamaiḥ — and regulative principles; śreyobhiḥ — by auspicious practices; vividhaiḥ — various; ca — also; anyaiḥ — others; kṛṣṇe — to Lord Kṛṣṇa; bhaktiḥ — devotional service; hi — indeed; sādhyate — is realized.
Translation: 
Devotional service unto Lord Kṛṣṇa is attained by charity, strict vows, austerities and fire sacrifices, by japa, study of Vedic texts, observance of regulative principles and, indeed, by the performance of many other auspicious practices.
Purport: 

Śrīla Viśvanātha Cakravartī explains the processes described here as follows. Dāna: donations given to Lord Viṣṇu and His devotees. Vrata: observing vows such as Ekādaśī. Tapas: renunciation of sense gratification for Kṛṣṇa’s sake. Homa: fire sacrifices dedicated to Viṣṇu. Japa: privately chanting the holy names of the Lord. Svādhyāya: study and recitation of Vedic texts such as the Gopāla-tāpanī Upaniṣad.