I usually learn them from the radio, or a recording, first. I listen to the song with earphones, and type the lyrics while I'm playing the song(I can type really fast!) The verses I don't know I wait until next time, and play it again. I do have a habit of leaving a CD on repeat all day long, and I love getting movie soundtracks with songs before the movie, so I can sing at the movie...*g*
And singing in the shower is great!! I wish I could sing in the shower(or sound as good as I sing in the shower) on Christmas Eve. I'm singing 'I Wonder as I Wander' a cappella (or however you spell that.) Wish me luck.