Here's another bit of advice: A good song should have some kind of a story arc. Whether it's a ballad or a description of how one is feeling, the end of the song should leave the listener in a different "place" than he was at the beginning of the song. That "place" could be the end of the story that's in the ballad, or it could be a change of feeling (happier or sadder or angrier or more hopeful than he felt before), or a deeper understanding of what the songwriter is describing. This is what another poster meant about how a song should have a beginning, a middle and an end.

If a song is simply something along the lines of: "I hurt. Boy, I hurt. I'm in pain all right. Yup, I hurt." ...it won't convey much (the depth of the pain, the reason for it, what if anything I might do to ease the pain) and it probably won't engender much sympathy or empathy UNLESS you use the tune, the accompaniment, changes in volume, vocal emphasis (improvisation or yodels or howls), etc., to invent a musical story arc rather than a lyrical story arc.

Even so, it's helpful to have the lyrics tell some sort of a story -- it can make the musical story arc even more powerful! The end can come back to the beginning (as in The House of the Rising Sun) or it can allude to the beginning (as in Saint James' Infirmary) for a sense of closure. Or it can take you on a journey (as in 59th Street Bridge Song, where the singer physically moves on down the street AND emotioally advances from where he's feelin' groovy to where ALL is groovy -- and note that the melody also advances as it modulates up a half-step!).

Don't underestimate the importance of a CHORUS or a REFRAIN. Repetition, repetition, repetition is good, good, good. :-)

Repetition is important in the structure of your verses, too: keep 'em consistent. If the rhyming scheme in your first verse is AABB, then the rhyming scheme in all your other verses ought to be AABB. The listener's brain hangs its hat on that kind of stuff, and expects it. Knocking its hat off in mid-song is generally not appreciated, and is as impolite as knocking someone's real hat off his head.