Good suggestions and advice so far. I'll add that I try to make sure my hands are warm. With juveniles, I use my hand to simulate a hide and let them stay there until they are ready to explore on their own. They grow to associate your hands with warmth and security.
It's also important to always remember that ball pythons are relatively low on the food chain and most predators come at them from above like birds of prey so when our hands come at them from above, it's normal for them to initially assume our hands are predators coming to snatch them up. It's easier to act with empathy when you have an understanding of their natural instincts and act accordingly to reduce their stress.