I used to mostly write the words first and find a tune later. Those songs are pretty wordy and the tunes are OK, but not too exciting.

A couple times, I've written words to fit a tune. They were OK, but it was harder for me.

Lately, I'm trying to do both at once. The words are a bit less 'precious' and more economical, the tunes are decent. It's harder, I think, but it also seems to make for a better song. I suspect I just have to write a whole lot more songs to improve.