The Beatles had the advantage of George Martin who, though classically trained, knew what a good song should sound like.
Martin had been given charge of a crappy minor sub-label of EMI's called Parlophone, which made novelty records. He wanted to turn it around and bring it to profitability. He was specifically looking for a hit rock and roll band, and discarded many before finding the Beatles. He figured that with a little tweaking he could make something different--and successful.
Martin made many suggestions for improving the groups music, giving them their distinct style. For instance, at their first recording session, he suggested that John and Paul change the tempo of their slow song, “Please Please me,” speeding it up and giving it more power. After hearing the result, he said to them, “Boys, you’ve just made your first #1.”