A song must move the story ahead. A song must take the place of dialogue. If a song halts the show, pushes it back, stalls it, the audience won't buy it; they'll be unhappy.

I don't care how good a song is - if it holds back the storyline, stalls the plot, your audience will reject it.

The songwriter mustn't fall in love with his own song. If it doesn't belong, he can't push it into a show. Let him save it; maybe it'll fit in another show.

Keep it in tune with the times, but don't write with the specific purpose of trying to create a hit. If you're doing it strictly to make money, you're crazy. There are easier ways to make money.