In plain words
Know this through reverent approach, sincere questioning, and service. Those with jñāna, the seers of tattva, will instruct you in jñāna.
Word for word
Know that by prostration, by thorough questioning, by service; the knowers, the seers of the truth, will teach you jñāna.
The commentators
Bhagavadgītābhāṣyam
तदेतत् विशिष्टं ज्ञानं तर्हि केन प्राप्यते इत्युच्यते —
तत् विद्धि विजानीहि येन विधिना प्राप्यते इति । आचार्यान् अभिगम्य, प्रणिपातेन प्रकर्षेण नीचैः पतनं प्रणिपातः दीर्घनमस्कारः तेन, ‘कथं बन्धः ? कथं मोक्षः ? का विद्या ? का चाविद्या ? ’ इति परिप्रश्नेन, सेवया गुरुशुश्रूषया एवमादिना । प्रश्रयेण आवर्जिता आचार्या उपदेक्ष्यन्ति कथयिष्यन्ति ते ज्ञानं यथोक्तविशेषणं ज्ञानिनः । ज्ञानवन्तोऽपि केचित् यथावत् तत्त्वदर्शनशीलाः, अपरे न ; अतो विशिनष्टि तत्त्वदर्शिनः इति । ये सम्यग्दर्शिनः तैः उपदिष्टं ज्ञानं कार्यक्षमं भवति नेतरत् इति भगवतो मतम् ॥ ३४ ॥
In plain words
Then by what is it reached, this knowledge of a different order? Here is the answer —
'Learn that' means: understand it, however it can be reached. Go to teachers, offer full prostration — falling down low before them, a complete bow — ask them respectfully: 'What is bondage? What is liberation? What is real knowledge, and what is ignorance?' — serve them, attend on them, and so on. Won over by such humility, teachers will actually teach, will actually tell you, that knowledge — but knowledge of a very particular kind, from real knowers. Because even among learned people, some genuinely have the habit of seeing the truth, and others simply don't — which is exactly why the verse specifically calls them 'seers of the truth.' Only knowledge taught by those who truly see rightly can actually accomplish anything; no other kind can. This is the Blessed Lord's own view.
Close to the Sanskrit
Then by what is this — that distinguished knowledge — attained? Thus it is said —
'That, know' — understand it, by whatever means it is attained. Having gone to teachers, by prostration — falling down low, thoroughly, that is prostration, a full extended bow — by that; by 'What is bondage? What is liberation? What is knowledge, and what is ignorance?' — by such respectful inquiry; by service, that is, by attending on the teacher, and the like. Won over by such humility, the teachers will teach, will tell, those knowledge — knowledge of the kind just qualified — the knowers; for even among the learned, some have, properly, the habit of seeing the truth, others do not; that is why he specifically qualifies them as 'seers of the truth'. Knowledge taught by those who are of right vision alone is capable of accomplishing the purpose, not any other — this is the Blessed Lord's own view.
Gītā Vāhini
“అర్జునా! ‘ఇట్టి పవిత్ర జ్ఞానము అందరికీ లభ్యమగునా?’ అని సంశయింతువేమో! లేక ‘ఇది లభించు ఉపాయమేది?’ అని ప్రశ్నింతువేమో! విను. ఈ పవిత్రమైన తత్త్వమును బదయగోరువారు తత్త్వవేత్తలగు మహనీయుల చెంతచేరి వారి చిత్తములు ప్రసన్నములగునట్లు చేసి, సమయ సందర్భములు చూచుకొని వారి మనస్సు నెరింగి మెలంగవలెను. సంశయములేవైనా స్ఫురించినపుడెల్లా ఇష్టమొచ్చినటుల ప్రశ్నించక, తరుణము, సమయము చక్కగా ఉన్న వేళ వాటిని శాంత మనస్కుడై మహనీయునికి తెలిపి దానిని నివారణ చేసుకొనవలెను కానీ ఊరకే పుస్తకములు బండ్లు బండ్లు చదివినంత మాత్రమున, ఉపన్యాసములు గంటలు కొట్టినట్లు చిలుకపలుకులు పలికిన గానీ, లేక దొంగ వేషములుగా కాషాయములు ధరించి ఊర్ధ్వదృష్టితో వుర్రూతలూగించిన గానీ అది జ్ఞాని లక్షణము కాదు.”
In plain words
“Arjuna! Perhaps you doubt, ‘Can such holy Jñāna be had by all?’ Or perhaps you ask, ‘What is the means of obtaining it?’ Listen. Those who wish to gain this holy tattva must go to great souls who are knowers of tattva, gladden their cittas, watch for the right time and occasion, and conduct themselves knowing their mind. Whenever doubts occur, one must not ask as one pleases; when the moment and the time are right, calm in mind, one must lay them before the great soul and have them removed. But merely reading books by the cartload, or reeling off lectures in parrot-talk as though striking bells, or putting on ochre robes as a false guise and thrilling people with an upturned gaze: none of that is the mark of a jñāni.”