Go through the song several times, feel the mood of the music, sense the whole meaning of the song and don’t get stuck with too much detail initially.
Listen to a recording, use it to feel the ‘architecture’ of the piece. try to work out where the ‘building bricks’ are for easy learning. Try not to use recordings too much, you can learn other’s mistakes that way!
Adopt clear learning paths: words and music.
Words: memorise the poem, write it out, look at the way the words are used as a poem and as a song, picture the moods/the story.
Music: check pitch/rhythm, examine intervals, patterns and phrases, sense harmonic structure/accompaniments, the links of musical ideas.
Use different strategies to learn the same things, i.e. dance as you sing, colour a picture as you sing.
Revisit the whole song, REHEARSE.
At the same time you must realise that you are learning how to build your instrument, so watch the technical things you are doing while you are memorising, posture, balance, timbre.
Don’t sing the notes, sing the music!
Concentrate your efforts in short regular bursts, not last minute panicking, make song maps, sing to the dog, sing to the tape recorder and Good luck!