Three ingredients for attaining bhāvollāsa

1. Hearing the works of Rūpa and Sanātana

The process of attaining bhāvollāsa love is described by Narottama Dāsa Ṭhākur in the first song of his famous "Moonbeam of Sacred Love" (Prema-bhakti-candrikā):

yugala-kiśora dhan, yena lakña-bāṇa hem, hena prema prakāśila yārā
jaya rūpa-sanātan, deha more sei dhan, se ratan mor gale hārā ||

prema-bhakti rīti jata, nija granthe subekata, kariyāchen dui mahāśay |
jāhāra śravaṇa haite, parānanda hay citte, yugala madhura rasāśray ||

The love of the Divine Couple is as pure as gold refined thousands of times.
May glory crown Rūpa and Sanātana, who revealed this treasure to the world.

O, please be kind and give me that treasure of love
and I will wear it as a pendant around my neck.
In their books, these two great ones
clearly showed all the intricacies of this sacred love.
Hearing their works produces the greatest joy in the heart
and shelter in the erotic rapture of the loving Couple.

2· Worshipping Rādhā

Raghunātha Dāsa writes in Sva-saṅkalpa-prakāśa-stotra:

anārādhya rādhā-padāmbhoja-reṇum anāśritya vrndāṭavīṁ tat-padāṅkām |
asambhāñya tad-bhāva-gambhīra-cittān kutaḥ śyāma-sindho rasāvagāhaḥ ||

Not ever having worshipped once the dust that sprinkles from Śrīmatī's lotus feet;
not having taken shelter even once of Vraja Dhām, marked with her dainty tread;
not ever having spoken with the souls so laden with a weighty love for her,
how foolish they who think that they can plunge into the secret sea of nectar that is Śyāma!

3· Greed for Kṛṣṇa rasa

In Padyāvalī 14, also quoted at CC, 2.8.11. it is said

kṛṣṇa-bhakti-rasa-bhāvita-matiḥ kriyatāṁ yadi kuto'pi labhyate |
tatra laulyam api mūlyam ekalaṁ janma-koṭi-sukṛtair na labhyate ||

O friend if you should find it anywhere, that heart absorbed in Kṛṣṇa rasa so rare,
be quick to buy, how much the soul's in need!
In that bazaar is posted just one price; millions of pious works will not suffice,
the cost is to be paid in coins of greed.