Answer
The general thinking is that you cannot put music to a poem. so songs... i am a terrible songwriter, and find it one of the hardest things in the world. bob dylan said it was the easiest, but thats only for him. there are no rules. speak from the heart, whether its happy, sad angry or whatever. try to write with your own slant, dont write cliches, dont use words cos they rhythm. dont feel you have to make complete sense (see rem, who are great, incidentally) and use emotive imagery. be honest, individual, and listen to the greats for inspiration, nick drake, ben harper, tom waits, billy holiday, etc etc etc. nice luck
