There is no definitive guidebook on how to pick the right partner, and even if there were, I'm way too dumb to write it.
One of the remarkable things about my career is that it has been marked by steady, incremental progress. No sudden spikes up, and no sudden downfalls, either.
There are things you do when you're writing that are so fun to do it's almost like they're private jokes that are amusing to you but no one else is going to enjoy them nearly as much and you worry you're going to have to take them out in the end.