For herbs on a stem like thyme, pinch the tip gently but firmly with thumb and index finger, using the opposite thumb and index finger pinch stem and slide leaves off of stem.
You will be left with a pile of small leaves for thyme but you can also do this with oregano, rosemary, marjoram, mint etc.
Place the opposite hand on top of the blade near the tip and using a rocking motion cut herbs into small pieces. You can rock back and forth, mincing all remaining herbs.
Alternatively you can mince herbs with a pair of dedicated kitchen scissors. This is a great technique for beginners or anyone without experience with a chefs knife.