Chap3: How do i select a threshold from the precision and recall vs threshold curve

Hi Ageron, I have another question although the last is still pending.
when I look at the precision versus recall curve. I can see that if my focus is on precision then a precision of 90% will mean a slap to recall at 60%. How do I use this information on the precision and recall versus threshold curve to select a threshold for fine-tuning?