Whatever item is suitable, that is accepted as very elevated. Just like Maharaja Pariksit. He simply listened to Sukadeva Gosvami. That is sravanam. And Sukadeva Gosvami simply narrated Srimad-Bhagavatam. This is kirtanam. Prahlada Maharaja simply contemplated - smaranam. Prthu Maharaja simply did deity worship - arcanam. Arjuna only remained as friend of Krishna - sakhyam. Hanuman remained only engaged in carrying out the order of Lord Ramacandra - dasyam. And Bali Maharaja surrendered everything to Krishna - atma-nivedanam. So, any devotee executing any one of the nine is transcendentally glorious.
Letter to Satsvarupa Maharaja, 19 January, 1975