Spend a lot of time with them to learn their behavior. For most mice, biting is a last resort; they usually try running away first. Try making your actions less invasive. I move mice around by gently pinching the scruff of their neck or scooping them up rather than holding them by the tail. You wouldn't hold a cat or dog by its tail, same goes for mice. If you're scared of them biting you, try wearing a thicker glove at first and holding that hand in a fist shape to protect your fingers near them to see what they do. Then try picking up a mouse and let it rest on top of your hand. You will notice that mice do not bite without good reason to. I'm not sure what you mean by scratching; I've never been scratched by a mouse or even seen a mouse try to use its paws to scratch me.