For me, producing music and the lyrics isn't a problem. Somehow, they just pop up in my head. Sometimes they fit, sometimes they don't. If they don't I end up composing two different songs. One based on the music, the other, based on the lyrics. Coming up with music for a lyric, I somehow find easier. But fitting in an existing lyric to music is hard so I tend to do some revisions to the lyrics like what iiholly does, so that I can fit it in.

As for writing lyrics, I find that focusing on one area like a certain topic helps- depending on what kind of music you're planning to write. Stop worrying how it will fit the song, or that the lyrics has to be good. Worry about it later. As iholly said: that's what revisions are for. To tell you the truth, writing lyrics only gets hard when you try to make an effort and be technical about it. Make it natural- like speaking or telling a story. I find that tapping on your emotion, your feminine side, your memories, your wit/ sense of humor etc. helps a great deal because you don't have to think too much and make an effort of what you write. It's like writing an essay- it's easier to write a topic that you know about, like you're favorite trip rather than writing an essay about nuclear physics. Let it flow man. Good luck writing those hits.