I agree with repetition. Doing a song over and over is the best way. I can "get" lyrics fast, but to memorize them I have to sing them over and over. (WITHOUT the words near me) And see what I need to work on.

TUNES are another thing though. I don't play an instrument, so I sing a capella. Getting the tune to a song takes me forever! It's one of those things that I can't change.