There are concrete examples of how a devotee discharged one of these services and achieved perfection. King Parīkṣit achieved the desired goal of life simply by hearing Śrīmad-Bhāgavatam. Śukadeva Gosvāmī achieved the desired goal of life simply by reciting Śrīmad-Bhāgavatam. Prahlāda Mahārāj became successful in his devotional service by always remembering the Lord. Lakṣmī, the goddess of fortune, was successful by engaging herself in massaging the lotus feet of the Lord. King Pṛthu became successful by worshiping in the temple. Akrūra became successful by offering prayers. Hanumān became successful by rendering personal service to Lord Rāmacandra. Arjuna became successful by being a friend of Kṛṣṇa. And Bali Mahārāj became successful simply by offering all of his possessions to Kṛṣṇa.
There are also examples of devotees who discharged all the different items together. In the Ninth Canto, 4th Chapter, 15th, 16th and 17th verses, of the Śrīmad-Bhāgavatam, there is a statement about Mahārāj Ambarīṣa, who followed every one of the devotional processes. In these verses, Śukadeva Gosvāmī says, "King Ambarīṣa first of all concentrated his mind on the lotus feet of Lord Kṛṣṇa and then engaged his speech in describing the pastimes and activities of the Lord. He engaged his hands in washing the temple of the Lord. He engaged his ears in hearing of the transcendental glories of the Lord. He engaged his eyes in seeing the beautiful Deity in the temple. He engaged his body in associating with the pure devotees of the Lord. (When you associate with someone you have to sit down together, eat together, etc.—and in this way the touch of your body with their body is inevitable. Ambarīṣa Mahārāj made his association only with pure devotees and did not allow his body to be touched by anyone else.) He engaged his nostrils in smelling the flowers and tulasī which were offered to Kṛṣṇa, and he engaged his tongue in tasting Kṛṣṇa-prasādam (food prepared specifically for offering to the Lord, the remnants of which are taken by the devotees). Mahārāj Ambarīṣa was able to offer very nice prasādam to Kṛṣṇa because he was a king and had no scarcity of finance. He used to offer Kṛṣṇa the most royal dishes and would then taste the remnants as Kṛṣṇa-prasādam. There was no scarcity in his royal style because he had a very beautiful temple wherein the Deity of the Lord was decorated with costly paraphernalia and offered high grade food. So everything was available, and his engagement was always completely in Kṛṣṇa consciousness."
The idea is that we should follow in the footsteps of great devotees. If we are unable to execute all the different items of devotional service, we must try to execute at least one of them, as exemplified by previous ācāryas. If we are engaged in the execution of all the items of devotional service, as was Mahārāj Ambarīṣa, then the perfection of devotional service is guaranteed from each one of these items. With the first complete engagement, one becomes automatically detached from material contamination, and liberation becomes the maidservant of the devotee. This idea is confirmed by Bilvamaṅgala Thākur: If one develops unalloyed devotion to the Lord, liberation will follow the devotee as his maidservant.
Śrīla Rūpa Gosvāmī says that the regulative principles of devotional service are sometimes described by authorities as the path of serving the Lord in opulence.