The Vrajavasis are the eternal associates of Sri Krishna and they have a very special bhava for Him.

When we hear about their bhava and how they express it, if we feel greedy to achieve the same bhava, then we are qualified for raganuga-bhajan.

Srila Rupa Goswamipad says this in B.R.S. –

tatra adhikārī—
rāgātmikāika-niṣṭhā ye vraja-vāsi-janādayaḥ |
teṣāṁ bhāvāptaye lubdho bhaved atrādhikāravān ||291||

The qualification for rāgānuga-bhakti is as follows:
That person who is greedy for attaining a bhāva similar to that of the inhabitants of Vraja—who are fixed solely in rāgātmika-bhakti—is qualified for rāgānuga-bhakti.

He has also described in detail how such a qualified devotee should perform raganuga-bhajan:

|| 1.2.294 ||
kṛṣṇaṁ smaran janaṁ cāsya preṣṭhaṁ nija-samīhitam |
tat-tat-kathā-rataś cāsau kuryād vāsaṁ vraje sadā ||294||

Remembering the Vṛndāvana form of Kṛṣṇa and His dear associates who have inclinations for service similar to one’s own, absorbing oneself in hearing topics related to them, one should always live in Vraja.

|| 1.2.295 ||
sevā sādhaka-rūpeṇa siddha-rūpeṇa cātra hi |
tad-bhāva-lipsunā kāryā vraja-lokānusārataḥ ||295||

Following after the inhabitants of Vraja, one should perform service in one’s physical body and in one’s siddha body, with a desire for a particular bhāva.

Srila Vishvanath Chakravartipad has explained the above two verses as follows –

In these two verses Srila Rupa Goswamipad has explained the proper way to perform raganuga-bhajan.

‘Preshtha’  (in  the  above  verse)  refers  to  our  Beloved  Sri  Nanda-Nandana  in  His  budding youth. We  should  worship  Sri  Krishna  in  this  form  alone,  but  at  the  same  time  we  should constantly remember His eternal associates who have similar desire as we and we should reside in Vraja-dhama in this manner. If possible we should physically live in some place in Vraja-dham such as Vrindavana etc. and in case we are incapable of doing so, it is our duty to live there at least in mind.

‘Sadhaka-form’  means  the  body  that  we  are  in  at  present,  and  ‘siddha-deha’  indicates  the  body that is worthy of serving in the divine world, that on which we should meditate upon. In this divine form (siddha-deha) we should serve under the command of Sri Radha, Lalita, Vishakha, Sri Rupa- manjari and other sakhis who are very dear to Sri Krishna and they wish to relish the sweet bhava of Sri Krishna.
In  the  sadhaka-body  we  should  serve  following  the  instructions  of  the  Goswamis such  as  Sri  Rupa  and  Sanatana.

This signifies that in siddha-svarupa we should perform seva mentally under the guidance of Sri Radha, Lalita, Vishakha, and Sri Rupa-manjari, while in sadhaka body we should do seva under the subjugation of the Vrajavasis such as Sri Rupa and Sanatana. This is our duty. Here ‘anusaratah’ does not mean ‘anukaran’ or imitation (we should not imitate the Goswamis or the  eternal  divine  associates),  rather  it  indicates  ‘anusaran’  –  which  means  –  we  should  serve according to their command and following their bhava.”

True,  on  the path of raganuga-bhakti,  meditating  on  the  divine  pastimes  is  the  main  sadhana,  however  in  the primary  stage  we  are  not  qualified  for  lila-smaran.
Therefore we should concentrate more on hearing, chanting and following the other rules of bhakti. Then as our consciousness gets more and more purified, we are drawn towards lila-smaranam. Slowly our smaranam becomes more intense.
Ultimately when we reach the zenith of bhajan, lila-smaranam naturally becomes the major part of bhajan.
We  should  note  that  all  the  parts  of  bhakti  mentioned  in  vaidhi-bhakti  are  useful  in raganuga-bhajan also.

Srila Rupa Goswamipad mentions this in the verse –  

|| 1.2.296 ||
śravaṇotkīrtanādīni vaidha-bhakty-uditāni tu|
yāny aṅgāni ca tāny atra vijñeyāni manīṣibhiḥ ||296||

The discriminating practitioners should accept the aṅgas which were mentioned in vaidhi-bhakti such as hearing and chanting as the aṅgas of rāgānuga-bhakti.

Here hearing and chanting also includes accepting the shelter of Sri Gurudeva’s lotus feet and other fundamentals of bhakti as well. We should realize that all the rules of bhakti that we have already mentioned, and they are the parts of vaidhi-bhakti – we should stick to them in raganuga-bhajan also.

If  we  do  not  obey  the  instructions  of  the  6  Goswamis  such  as  Sri  Rupa  Goswami, Sanatana Goswami etc., how can we say we are surrendered unto them? Then how can we follow in their footsteps?

The  serious  devotees  should  practice  only  those  rules  that  are in  accordance with  their  bhava  and  never  do  what  is  contrary  to  it  –  such  as aham-grahopasana, mudra, nyas, meditating  on  Dwaraka,  worshiping Sri  Rukmini  etc.
Although the agama-shastras mention these processes of bhakti, a raganuga-sadhaka should not perform them.

Raganuga practice has two limbs – external and internal.

External  practice  is  done  with  our sadhaka-body,  while  we  perform  internal  sadhana  by  meditating  on  our  siddha-deha.

In the sadhaka-body we should hear, chant, forsake material pleasures, and serve The Deities with actual ingredients. We  should  meditate  on  our  siddha-deha  and  serve  Sri  Krishna  Who  is  our  Beloved with  this  body  for  only  the  siddha-deha  is  worthy  of  serving  the  divine  Couple. We  should  seek refuge  of Srimati  Radharani Who is  the object  of our  love  and  surrender  unto Her  and  Her  dear ones. It is our duty to strive for that brilliant rasa and following the instructions of Sri Rupa-manjari we should collect objects in meditation for internal seva and serve the Divine Couple as the time and situation demands.

“bahya antar ihar dui to sadhan, bahya –
sadhak-dehe kore shraban kirtan.
mone – nija siddha-deha koriya bhabon,
ratridine kore braje radha-krishner seban.”
(C.C. Madhya.22.89-90)

Meaning  –  “Raganuga  bhajan  comprises  of  two  practices  –  external  and  internal. Externally,  we should hear and chant, while we should meditate on our siddha deha and serve Sri Radha-Krishna in Vraja-dham all day and night.”

– Srila Ananta das Babaji (Raganuga-bhakti-tattva-vijnana)