I used to start with the lyrics first, but I found that the music comes a lot easier and steadily to me than the lyrics, so I have a dearth of music with no lyrics. Usually I'd say that I write music then lyrics, but frequently nowadays I write both at the same time.

Basically my method nowadays is I have a few lyrical ideas, and a few musical ideas floating around in my head, and then I just randomly become inspired and bang it all out in about 15 minutes. It happens a lot now.

I'd just say keep at both sides of equation separately until they start to work together, and practice writing songs. I have lots of songs I've written that I don't think I'll ever play for anyone just because they are more like practice and I don't think I could memorize that many songs. Then you just take your favorite ones and roll out with those ones.