One the first, Heartbeat - WW had a title in mind and asked if I had any ideas. I threw a couple at her and she came up w/ the first scene and off we went. We don't plan too far ahead - we wait for the other to write the chapter and see what inspires us. We have no idea what the other is writing until we get the completed chapter.
On the second With Deadly Intent - it took forever to come up w/ a title, which she finally did - she's the best at that. She heard the song in the first scene and the entire story came after they discuss the song on a stakeout. Each chapter was a complete surprise to the other.
This next one is promising to be something different and hopefully good.
thanks for the feedback.