Memorising the piece is the start. You'll be hard pushed to interpret a song as you read it.
Having it in the memory you can then experiment and consider the placement and emphasis of words based on your understanding of the song and how you think it should be told.
Then, hopefully, you can remember that preferred rendering and go out and sing. You might still, after a performance think some part wasn't quite how you wanted it, think of an improvement and do it different next time.
A recording, even done at home can be very revealing and help with refinement.

Of course you don't have to bother with any of this. They'll still say 'well sung'.