From Srila Prabhupada’s letter to Upendra — Los Angeles 13 November, 1968:
You can celebrate Rasa-lila by having nice kirtana and prasadam distribution, that is our way of celebrating.
From Srila Prabhupada’s letter to Krsna dasa — London 7 November, 1969:
To celebrate the Rasa Lila Ceremony decorate the Deities very nicely with flowers; as many as possible, ornaments, garlands, nice light demonstration, and much distribution of prasadam.