Thinking of Krsna twenty-four hours is first-class meditation. You are seeing Krsna here, standing with Radharani. And if you see always, then you naturally you get impression of Krsna within the heart. Those who are engaged in service, just like they are offering this foodstuff, Krsna. They have prepared this foodstuff very nicely, thinking that “Krsna will eat. Let us do it very cleanly and attentively.” And whatever they can offer, first-class thing… That is meditation, because they are thinking of Krsna, “This foodstuff will be taken by Krsna. This dress will be used by Krsna. These flowers will be offered to the lotus feet of Krsna.” Real meditation is this. And that is the first-class yoga.
Srila Prabhupada, Talk on Srimad-Bhagavatam 3.25.31 – December 1, 1974, Bombay