Well...
1. listen to it over and over till my family is sick of me
2. take it downstairs and type out the lyrics on the computer--handwriting is a lost art for me.
3. listen, work out chords or modal equivalent, and decide if I can effectively sing it in the same key I'm hearing.
4. make the necessary adjustments till key and accompaniment feel right
5. Play it and play it and play it till I'm sick of it.
Its a funny thing...I pretty much have to get lyrics on paper to learn them--but in learning to play a tune (ie not a song), it comes quicker if I learn it all or mostly by ear. If I try to learn it depending heavily on the printed notation, it takes forever to commit it to memory.
Bill