The rules concentrate on the Score and Downtime and don’t talk much about Free Play apart from calling it out as part of the game structure.
How much time do you tend to spend in ‘Free Play’ during your games? Would you like more or less?
What kind of things do you do in ‘Free Play’ and when do you decide that it probably belongs in a Score rather than Free Play?
Cheers
We spend about 25% of time in free play. A few scores in this is now mostly scenes with other factions, contacts and entities based on previous fallout from scores and downtime. To give an example, information from a bluecoat contact lead to the death of a few bluecoats, and they are angry and want a word (interestingly the exact same thing happened in The Magpies podcast).
In another case someone from a players past came back to say hello, threaten them, and see if they wanted to help out another faction. The answer was no so this was not connected to a scene or even gathering information - just a RP scene.
If we were to include gathering information and the more freewheeling role-playing part of downtime then this would make up nearly 40%. It is worth noting that the diagram of scores, downtime and FreePlay at the start of the book is purposefully designed with blurred lines between them 
I talked to my players in the last session and and they did not feel the balance was wrong but they wanted to slow down during the downtime actions to stretch those more into role-playing scenes.
We have so far only had one instance of what in the theatre we would call a soft start - free scenes turned into gathering information and almost inadvertently the score started. We did an engagement roll but in retrospect it probably should have been skipped as I was very relieved when it matched the actual situation that we were in!
We spend a fairly big chunk of the game (maybe 25%?) in free play as I’m blessed with very creative players with tons of things they want to do. I think there’s no amount of time that’s too much or too little free play; adjust it for what’s right for that particular group of players. If they have a ton of things they want to do in free play, they can spend most of the session in free play. If they don’t know what to do during free play or simply prefer the action, cut out all of free play.
My players do all sorts of things in free play that could also be covered in flashbacks, e.g. when they gather info, or they do things that should actually have been done during the previous downtime phase, namely acquiring assets.
Usually I know ahead of a session what scenes are going to be scores; it’s the part I prep. Any prolonged scenario consisting of the several challenges the pcs must overcome that involve real risk constitutes a score.